Margaret Hilda Thatcher, Baroness Thatcher, LG, OM, PC, FRS (born 13 October 1925) served as Prime Minister of the United Kingdom from 1979 to 1990 and Leader of the Conservative Party from 1975 to 1990. She is the only woman to have held either post.

Born in Grantham in Lincolnshire, United Kingdom, she read chemistry at Somerville College, Oxford and later trained as a barrister. She won a seat in the 1959 general election, becoming the MP for Finchley as a Conservative. When Edward Heath formed a government in 1970, he appointed Thatcher Secretary of State for Education and Science. Four years later, she backed Keith Joseph in his bid to become Conservative Party leader but he was forced to drop out of the election. In 1975 Thatcher entered the contest herself and became leader of the Conservative Party. At the 1979 general election she became Britain's first female Prime Minister. In her foreword to the 1979 Conservative manifesto, Thatcher had written of "a feeling of helplessness, that a once great nation has somehow fallen behind." She entered 10 Downing Street determined to reverse what she perceived as a precipitate national decline, characterised by a combination of high inflation, high unemployment and stagnant or slow growth. Her political philosophy and economic policies emphasised deregulation, particularly of the financial sector, flexible labour markets, and the selling off of state owned companies. Amid a recession and high unemployment, Thatcher's popularity declined, though economic recovery and the 1982 Falklands War brought a resurgence of support and she was re-elected in 1983. She took a hard line against trade unions, survived the Brighton hotel bombing assassination attempt and opposed the Soviet Union (her tough-talking rhetoric gained her the nickname the "Iron Lady"); she was re-elected for an unprecedented third term in 1987. The following years would prove difficult, as her Poll tax plan was largely unpopular, and her views regarding the European Community were not shared by others in her Cabinet. She resigned as Prime Minister in November 1990 after Michael Heseltine's challenge to her leadership of the Conservative Party. Thatcher's tenure as Prime Minister was the longest since that of Lord Salisbury and the longest continuous period in office since Lord Liverpool in the early 19th century. She was the first woman to lead a major political party in the United Kingdom, and the first of only three women to hold any of the four great offices of state. She holds a life peerage as Baroness Thatcher, of Kesteven in the County of Lincolnshire, which entitles her to sit in the House of Lords.

Margaret Hilda Roberts was born on 13 October 1925 to Alfred Roberts, originally from Northamptonshire, and his wife, the former Beatrice Ethel Stephenson from Lincolnshire. Thatcher spent her childhood in the town of Grantham in Lincolnshire, where her father owned two grocery shops. She and her older sister Muriel (born 1921, Grantham; died December 2004; married name Cullen) were raised in the flat above the larger of the two located near the railway line. Her father was active in local politics and religion, serving as an Alderman and Methodist lay preacher. He came from a Liberal family but stood — as was then customary in local government — as an Independent. He lost his post as Alderman in 1952 after the Labour Party won its first majority on Grantham Council in 1950. Margaret Roberts was brought up a strict Methodist by her father. Having attended Huntingtower Road Primary School, she won a scholarship to Kesteven and Grantham Girls' School. Her school reports show hard work and commitment, but not brilliance. Outside the classroom she played hockey and also enjoyed swimming and walking. Finishing school during the Second World War, she applied for a scholarship to attend Somerville College, Oxford, but was only successful when the winning candidate dropped out. She went to Oxford in 1943 and studied Natural Sciences, specialising in Chemistry. She became President of the Oxford University Conservative Association in 1946, the third woman to hold the post. At Oxford she read Friedrich von Hayek's recently published (1944) The Road to Serfdom. " I cannot claim that I fully grasped the implications of Hayek's little masterpiece at this time, [but] at this stage it was the.. unanswerable criticisms of socialism in The Road to Serfdom which had an impact." In 1946 Roberts took the Final Honour School examination, graduating with a Second Class Bachelor of Arts degree. She subsequently studied crystallography and received a postgraduate BSc degree in 1947. Three years later, in 1950, she achieved a Master of Arts advanced degree, according to her entitlement as an Oxford BA of seven years' standing since matriculation.

Following graduation, Roberts moved to Colchester in Essex, to work as a research chemist for BX Plastics. During this time she joined the local Conservative Association and attended the party conference at Llandudno in 1948, as a representative of the University Graduate Conservative Association. She was also a member of the Association of Scientific Workers. In January 1949, a friend from Oxford, who was working for the Dartford Conservative Association, told her that they were looking for candidates. After a brief period, she was selected as the Conservative candidate, and she subsequently moved to Dartford, Kent, to stand for election as a Member of Parliament. To support herself during this period, she went to work for J. Lyons and Co., where she helped develop methods for preserving ice cream and was paid £500 per year.

At the 1950 and 1951 elections, she fought the safe Labour seat of Dartford. Although she lost out to Norman Dodds, she reduced the Labour majority in the constituency by 6,000. She was, at the time, the youngest ever female Conservative candidate and her campaign attracted a higher than normal amount of media attention for a first time candidate. While active in the Conservative Party in Kent, she met Denis Thatcher, whom she married in 1951, conforming to his Anglicanism. Denis was a wealthy divorced businessman who ran his family's firm; he later became an executive in the oil industry. Denis funded his wife's studies for the Bar. She qualified as a barrister in 1953 and specialised in taxation. In the same year her twin children Carol and Mark were born, delivered by Caesarean section while their father watched a Test match at the Oval. With a mother climbing the political ladder, the children were left to a nanny. "My mother was prone to calling me by her secretaries' names and working through each of them until she got to Carol", recalled her daughter.

Thatcher began to look for a safe Conservative seat in the mid-1950s and was narrowly rejected as candidate for the Orpington by-election in 1955, and was not selected as a candidate in the 1955 election. She had several further rejections before being selected for Finchley in April 1958. She won the seat after hard campaigning during the 1959 election and was elected as a Member of Parliament (MP). Her maiden speech was in support of her Private Member's Bill (Public Bodies (Admission to Meetings) Act 1960) requiring local councils to hold meetings in public, which was successful. In 1961 she went against the Conservative Party's official position by voting for the restoration of birching. Within two years, in October 1961, she was given a promotion to the front bench as Parliamentary Undersecretary at the Ministry of Pensions and National Insurance. She held this post throughout the administration of Harold Macmillan, until the Conservatives were removed from office in the 1964 election. When Sir Alec Douglas-Home stepped down, Thatcher voted for Edward Heath in the leadership election of 1965 over Reginald Maudling. She was promoted to the position of Conservative spokesman on Housing and Land; in this position, she advocated the Conservative policy of allowing tenants to buy their council houses. The policy would prove to be popular. She moved to the Shadow Treasury team in 1966. As Treasury spokesman, she opposed Labour's mandatory price and income controls, which she argued would produce contrary effects to those intended and distort the economy.

Thatcher established herself as a potent conference speaker at the Conservative Party Conference of 1966, with a strong attack on the high-tax policies of the Labour Government as being steps "not only towards Socialism, but towards Communism". She argued that lower taxes served as an incentive to hard work. Thatcher was one of few Conservative MPs to support Leo Abse's Bill to decriminalise male homosexuality and voted in favour of David Steel's Bill to legalise abortion, as well as a ban on hare coursing. She supported the retention of capital punishment and voted against the relaxation of divorce laws. In 1967 she was selected by the Embassy of the United States in London to participate in the International Visitor Leadership Program (then called the Foreign Leader Program), a professional exchange programme in which she spent about six weeks visiting various U.S. cities, political figures, and institutions such as the International Monetary Fund. Later that year, Thatcher joined the Shadow Cabinet as Shadow Fuel spokesman. Shortly preceding the 1970 general election, she was promoted to Shadow Transport and, finally, Education.

When the Conservative party under Edward Heath won the 1970 general election, Thatcher became Secretary of State for Education and Science. In her first months in office, Thatcher came to public attention as a result of the administration of Edward Heath's decision to cut spending. She gave priority to academic needs in schools, and imposed public expenditure cuts on the state education system, resulting in, against her private protests, the abolition of free milk for school-children aged seven to eleven. She believed that few children would suffer if schools were charged for milk, however she agreed to give younger children a third of a pint, daily, for nutritional purposes. This provoked a storm of protest from the Labour party and the press, and led to the unflattering moniker "Margaret Thatcher, Milk Snatcher". Of the experience, Thatcher later wrote in her autobiography, "I learned a valuable lesson. I had incurred the maximum of political odium for the minimum of political benefit." She successfully resisted the introduction of library book charges. She did not volunteer spending cuts in her department, contrary to her later beliefs. Her term was marked by support for several proposals for more local education authorities to close grammar schools and to adopt comprehensive secondary education. Thatcher, committed to a tiered secondary modern / grammar school system of education, was determined to preserve grammar schools, which prepared more students for admission to universities. She abolished Labour's commitment to comprehensive schooling, and instead left the matter to local education authorities.

The Heath government experienced many difficulties between 1970 and 1974. The government executed a series of reversals in its economic policies, dubbed "U-turns". The Conservatives were defeated in the February 1974 general election, and Thatcher's portfolio was changed to Shadow Environment Secretary. In this position she promised to abolish the rating system that paid for local government services, which was a favoured policy proposal within the Conservative Party for many years. Thatcher thought that the Heath Government had lost control of monetary policy — and had lost direction. After her party lost the second election of 1974 in October, Thatcher, determined to change the direction of the Conservative party, challenged Heath for the Conservative party leadership. She promised a fresh start, and her main support came from the Conservative 1922 Committee. Unexpectedly, she defeated Heath on the first ballot, and he resigned the leadership. On the second ballot, she defeated Heath's preferred successor, William Whitelaw, and became Conservative Party leader on 11 February 1975. She appointed Whitelaw as her deputy. Heath remained disenchanted with Thatcher to the end of his life for what he, and many of his supporters, perceived as her disloyalty in standing against him.

Now that the Heath government had fallen, Thatcher, "renewed [her] reading of the seminal works of liberal economics and conservative thought. I also regularly attended lunches at the Institute of Economic Affairs where Ralph Harris, Arthur Seldon and all those who had been right, when we in Government had gone so badly wrong..were busy marking out a new path for Britain. " (The IEA, a think tank founded by the poultry magnate Antony Fisher, the man who brought battery farming to Britain and a disciple of Friedrich von Hayek, had become the ideas factory of a new British Conservatism. Thatcher began visiting the IEA and reading its publications during the early sixties.) Thatcher would now become the face of the ideological movement that felt the opposite of reverence for the welfare state Keynesian economics they believed was terminally weakening Britain. " Whatever the question the institute's pamphlets posed, their answer was basically identical: less government, lower taxes, more freedom for business and consumers." 

In these years Thatcher began to work on her image, specifically her voice and screen image. "The hang-up has always been the voice" wrote the critic Clive James, in The Observer. "Not the timbre so much as, well, the tone - the condescending explanatory whine which treats the squirming interlocutor as an eight-year-old child with learning deficiencies. News Extra rolled a clip from May 1973 demonstrating the Thatcher sneer at full pitch. She sounded like a cat sliding down a blackboard." She worked to change this image and James acknowledged: "She's cold, hard, quick and superior, and smart enough to know that those qualities could work for her instead of against."

Thatcher appointed many of Heath's supporters to the Shadow Cabinet, for she had won the leadership as an outsider and then had little power base of her own within the party. Thatcher had to act cautiously to convert the Conservative Party to her monetarist beliefs. She reversed Heath's support for devolved government for Scotland. On 19 January 1976, she made a speech in Kensington Town Hall in which she made a scathing attack on the Soviet Union. The most famous part of her speech ran:

The Russians are bent on world dominance, and they are rapidly acquiring the means to become the most powerful imperial nation the world has seen. The men in the Soviet Politburo do not have to worry about the ebb and flow of public opinion. They put guns before butter, while we put just about everything before guns.

In response, the Soviet Defence Ministry newspaper Krasnaya Zvezda (Red Star) gave her the nickname "Iron Lady". She took delight in the name and it soon became associated with her image as having an unwavering and steadfast character. She was later nicknamed "Attila the Hen" as well.

In an interview in January 1978,on the television current-affairs programme World in Action Thatcher raised the prospect of the number of Pakistani and Commonwealth Britons doubling to four million by the end of the century, remarking: "People are really rather afraid that this country might be swamped by people with a different culture". Thatcher was condemned for the language and content of her remarks by Callaghan and Healey, by bishops, by the Liberal leader David Steel and, in private, by some shadow cabinet colleagues. Enoch Powell expressed his 'hope and relief' at her words. "By the sixties and seventies, with British imperial pride receding fast and a debate about national decline established in its place, Commonwealth immigration could look, to a certain kind of British patriot, less like a healthy post-imperial exchange and more like a national defeat: an invasion of territory of the kind previously mounted by Britain against other states." Thatcher received 10,000 letters thanking her for raising the subject of immigration, and the Conservatives, previously level with Labour on 43% in opinion polls, took a 48% to 39% lead. "Before my interview, the opinion polls showed us level-pegging with Labour. Afterwards, they showed the Conservatives with an eleven-point lead...It provided a large and welcome boost at an extremely difficult time."

In spite of economic recovery in the late seventies and recovery in average disposable income from 1977 onwards, the Labour Government was faced with unease about the direction of the country, and eventually, 'a sudden nationwide revolt against the Social Contract, during the winter of 1978–79, popularly dubbed the "Winter of Discontent". 'Party in grip of mild euphoria,' wrote Thatcher's adviser John Hoskyns in his diary on 18 January, 'because country beset by strikes..' The Conservatives attacked the government's unemployment record, and used advertising hoardings with the slogan Labour Isn't Working to assist them. When the rough poster was shown to Thatcher, "She stared at it for a long time; the convention in party propaganda was not to mention the opponent directly. 'Why is the biggest thing on the poster the name of the opposition? We're advertising Labour,' she said. Tim Bell (Saatchis managing director) and Maurice Saatchi replied, almost in unison, 'No, we're demolishing Labour.' " Denis Healey criticised Saatchi & Saatchi for having staged the photograph with Saatchi employees. In fact the advertisers had used a group of twenty Young Conservatives from South Hendon "photographed over and over". The Saatchi campaign unsettled Labour at a crucial moment. Unemployment would often be much worse in the next decade without bringing down Thatcher's government.

In the run up to the 1979 General Election, most opinion polls showed that voters preferred James Callaghan of the Labour party as Prime Minister, even as the Conservative Party maintained a lead in the polls. After a successful motion of no confidence in spring 1979, Callaghan's Labour government fell. The Conservatives would go on to win a 44-seat majority in the House of Commons and Margaret Thatcher became the United Kingdom's first female Prime Minister. Thatcher became Prime Minister on 4 May 1979. Arriving at 10 Downing Street, she said, in a paraphrase of St. Francis of Assisi:

Where there is discord, may we bring harmony. Where there is error, may we bring truth. Where there is doubt, may we bring faith. And where there is despair, may we bring hope.

Thatcher was incensed by one contemporary view within the British Civil Service that its job was to manage the UK's decline from the days of Empire and she wanted the country to assert a higher level of influence and leadership in international affairs. She represented the newly energetic right wing of the Conservative Party and advocated greater independence of the individual from the state and less government intervention. She became a very close ally, philosophically and politically, with President of the United States Ronald Reagan, elected in 1980. During her tenure as Prime Minister she was said to need just four hours' sleep a night. Thatcher's political and economic philosophy emphasised reduced state intervention, free markets, and entrepreneurialism. She wished to end what she felt was excessive government interference in the economy, and therefore privatized many nationally-owned enterprises and sold public housing to tenants at cut prices. Influenced by monetarist thinking as espoused by Milton Friedman, she began her economic reforms by increasing interest rates to try to slow the growth of the money supply and thereby lower inflation. She also placed limits on the printing of money and legal restrictions on trade unions, in her quest to tackle inflation and trade union disputes, which had bedevilled the UK economy throughout the 1970s. In accordance with her anti-interventionist views, she introduced cash limits on public spending and reduced expenditures on social services such as education (until 1987) and housing. Later, in 1985, as a deliberate snub, the University of Oxford voted to refuse Thatcher an honorary degree in protest against her cuts in funding for higher education.

At the time, some Heathite Conservatives in the Cabinet, the so-called "wets", expressed doubt over Thatcher's "dry" policies. Civil unrest in Britain resulted in the British media discussing the need for a policy u-turn. At the 1980 Conservative Party conference, Thatcher addressed the issue directly, armed with a speech written by the playwright Ronald Millar which included the lines: "You turn if you want to. The lady's not for turning!" Thatcher lowered direct taxes on income and increased indirect taxes instead, as the Early 1980s recession deepened, despite concerns expressed in a letter from 364 leading economists. Unemployment soared, and in December 1981 Thatcher's job approval rating fell to 25%, the lowest of her entire premiership, a lower rating than recorded for any previous prime minister, although she remained more popular than her party. A month later, in January 1982, the worst post-war slump bottomed out, inflation dropped to 8.6% from an earlier high of 18%, and interest rates fell, although unemployment was now in excess of 3,000,000 for the first time since the 1930s. Thatcher's job approval rating recovered to 32%. By 1983, overall economic growth was stronger and inflation and mortgage rates were at their lowest levels since 1970, though manufacturing output had dropped 30% from 1978 and unemployment had more than doubled to 3.6 million.

The term "Thatcherism" came to refer to her policies as well as aspects of her ethical outlook and personal style, including moral absolutism, nationalism, interest in the individual, and an uncompromising approach to achieving political goals. American author Claire Berlinski, who wrote the biography There Is No Alternative: Why Margaret Thatcher Matters, argues repeatedly throughout the volume that it was this Thatcherism, specifically her focus on economic reform, that set the United Kingdom on the path to recovery and long term growth.

The hunger strike was begun by a number of Provisional IRA and Irish National Liberation Army prisoners in Northern Ireland's Maze Prison to regain the status of political prisoners which had been revoked five years earlier under the preceding Labour government. Bobby Sands began the strike, saying that he would fast until death unless prison inmates won concessions over their living conditions. Thatcher refused to countenance a return to political status for the prisoners, famously declaring "Crime is crime is crime; it is not political" and felt that Britain should not negotiate with terrorists. However, despite holding this view in public, the British government made private contact with republican leaders in a bid to bring the hunger strikes to an end. After nine more men had starved to death and the strike had ended, some rights were restored to paramilitary prisoners, but official recognition of political status was not granted. Later that year, Thatcher and Irish Taoiseach Garret FitzGerald established the Anglo-Irish Inter-Governmental Council, which would act as a forum for meetings between the two governments. On 15 November 1985, Thatcher and FitzGerald signed the Hillsborough Anglo-Irish Agreement; the first time a British government gave the Republic of Ireland an advisory role in the governance of Northern Ireland.

On 2 April 1982, the ruling military junta in Argentina invaded the Falkland Islands and South Georgia, British overseas territories that Argentina claimed. The following day, Thatcher sent a naval task force to recapture the islands and eject the invaders. The conflict escalated from there, evolving into an amphibious and ground combat operation. Argentina surrendered on 14 June and the operation was hailed a great success, notwithstanding the deaths of 255 British servicemen and three Falkland Islanders. 649 Argentinians also died, half of them after the cruiser ARA General Belgrano was torpedoed by HMS Conqueror. Victory in the South Atlantic brought a wave of patriotic enthusiasm and support for the government. Thatcher's personal approval rating rose from 30% to 59%, as measured by Mori, and from 29% to 52%, according to Gallup. Conservative support climbed from 27% to 44%, while Labour's slipped from 34% to 27%. On 26 July 1982, a service of thanksgiving for the victory was held in St Paul's Cathedral, and the Archbishop of Canterury Robert Runcie delivered a sermon which asked the congregation to share the grief of both British and Argentinian mourners alike. Thatcher did not approve. Privately, according to an aide, she agreed with Edward du Cann, Julian Amery and other Tory MPs who saw the Runcie sermon as proof that the Government still had many enemies who deserved denouncing. "Not the least of the Falklands after-effects was the start of a long, sometimes venomous distancing, which continued through the 1980s, between the leading representatives of Church and state."

Economic recovery from the spring of 1982 bolstered the Thatcher government's popularity, and although many contemporary commentators saw the ensuing national poll as a khaki election that was decided by the "Falklands factor", the war had produced a disaggregated boost to Conservative support of no more than 3% for 3 months, suggesting Thatcher's sustained improvement was due instead to successful macroeconomic management. She also faced a divided opposition: Labour was bitterly split; the party had responded to the New Cold War by moving to the left and adopting a policy of unilateral nuclear disarmament, and had lost many senior leaders to the new Social Democratic Party in alliance with the Liberal Party, preventing the formation of an electoral pact against the Conservatives. Labour leader Michael Foot was a left-winger and generally regarded as unelectable, while Conservatives viewed Thatcher as 'their greatest electoral asset'. In the June 1983 general election, the Conservatives won 42.4% of the vote, the Labour party 27.6% and the Alliance 25.4% of the vote. Although the Conservatives' share of the vote had fallen slightly (1.5%) since 1979, Labour's vote had fallen by far more (9.3%) and under the first past the post system, the Conservatives won a landslide victory with a massive majority. This resulted in the Conservative party having an overall majority of 144 MPs.

The policy of privatisation has been called "a crucial ingredient of Thatcherism". After the 1983 election the sale of large state utilities to private companies accelerated. British Petroleum was privatised in stages in October 1979, September 1983 and November 1987; British Aerospace in January 1981 and 1985; the government share in British Sugar in July 1981; Cable and Wireless in November 1981; Amersham International and National Freight Corporation in February 1982; Britoil in November 1982 and August 1985; Associated British Ports in February 1983; Jaguar in July 1984; British Telecom in November 1984; the National Bus Company in October 1986; British Gas in December 1986; British Airways in February 1987; the Royal Ordnance in April 1987; Rolls-Royce in May 1987; the British Airports Authority in July 1987; the Rover Group in August 1988; British Steel in December 1988; the Regional Water Authorities in November 1989; Girobank in July 1990; and the National Grid in December 1990. In 1983 Thatcher also broke up and privatised British Shipbuilders, which had been amalgamated and nationalised by Callaghan in 1977 in the lean times following the 1973 oil crisis, and which still employed 86,000 people building naval and commercial vessels, many in the north-east of England. Few of the privatised shipyards subsequently survived competition against East Asian cheap labour, with the single largest private sector group, BVT, now employing a fraction of the nationalised group's number, just over 7,000 people working on Navy contracts in the Clyde and Portsmouth yards.

The process of privatisation, especially the preparation of nationalised industries for privatisation, was associated with marked improvements in performance, particularly in terms of labour productivity. But it is not clear how far this can be attributed to the merits of privatisation itself. Marxian economist Andrew Glyn believed that the "productivity miracle" observed in British industry under Thatcher was achieved not so much by increasing the overall productivity of labour as by reducing workforces and increasing unemployment. A number of the privatised industries, such as gas, water and electricity, were natural monopolies for which privatisation involved little increase in competition. Furthermore, the privatised industries that underwent improvements often did so while still under state ownership. For instance, British Steel made great gains in profitability while still a nationalised industry under the government-appointed chairmanship of Ian MacGregor, who faced down trade-union opposition to close plants and more than halve the workforce. Regulation was also greatly expanded to compensate for the loss of direct government control, with the foundation of regulatory bodies like Ofgas, Oftel and the National Rivers Authority. Overall, there was no clear pattern between the degree of competition, regulation and performance among the privatised industries. While the output and profits of the privatised companies grew, margins increased, and employment declined, the exact relationship of these changes to privatisation is uncertain. Many people took advantage of share offers, although many sold their shares immediately for a quick profit and therefore the proportion of shares held by individuals rather than institutions did not increase. By the mid 1980s, the number of individual stockholders had tripled, and the Thatcher government had sold 1.5 million publicly owned housing units to their tenants.

The privatisation of public assets was combined with deregulation of finance in an attempt to fuel economic growth. Notably, in 1979 Geoffrey Howe abolished Britain's exchange controls to allow more capital to seek profits overseas and the Big Bang of 1986 removed many restrictions on the activities of the London Stock Exchange. The Thatcher government encouraged the growth of the financial and service sectors to replace Britain's ailing manufacturing industry. Susan Strange called this new financial growth model, flourishing in Britain and America under Thatcher and Reagan, "casino capitalism" - as speculation and trading in financial claims became a more important part of the economy than industry.

Thatcher was committed to reducing the power of the trade unions, whose leadership she accused of undermining parliamentary democracy and economic performance through paralysing strike action. Several unions launched strikes in response to legislation introduced to curb their power, but resistance eventually collapsed. Only 39% of union members voted for Labour in the 1983 general election. According to the BBC, Thatcher "managed to destroy the power of the trade unions for almost a generation." The number of stoppages across the United Kingdom peaked at 4,583 in the crisis year of 1979 that brought Thatcher to power, with over 29 million working days lost. 1984, the great year of industrial confrontation with the National Union of Mineworkers (NUM), saw 1,221 stoppages and over 27 million working days lost. Stoppages then fell steadily through the rest of Thatcher's premiership, to 630 by 1990, with under 2 million working days lost, and continued to fall thereafter. Trade union membership also fell, from over 12 million in 1979 to 8.4 million in 1990. The miners' strike was the climax of the confrontation between the unions and the Thatcher government. In March 1984 the NUM ordered a strike, without a national ballot, in opposition to National Coal Board proposals to close 20 pits out of 174 state-owned mines and cut 20,000 jobs out of 187,000. Two-thirds of the country's miners downed tools. Thatcher refused to meet the union's demands, and said: "We had to fight the enemy without in the Falklands. We always have to be aware of the enemy within, which is much more difficult to fight and more dangerous to liberty." Violence was common on the picket lines during the miners' strike; controversial police tactics were used against strikers. The strike resulted in at least three deaths. Two miners, Joe Green and David Jones, were crushed to death by lorries while picketing. Two miners, Dean Hancock and Russell Shankland, were sentenced to eight years' imprisonment for the manslaughter of taxi driver David Wilkie who was taking a working miner to his colliery. Some 20,000 people were injured in the course of the strike. 11,300 miners and their supporters were arrested and charged with criminal offences.

The NUM's failure to ballot and the picket line violence and intimidation cost the strike public support. A MORI poll in June 1984 found that 41% of people backed the Coal Board, and 35% the miners. By August support for the Board had risen to 46%, while support for the miners had fallen to 30%. The position remained unchanged at the end of the year. The miners' strike also split the trade union movement, with lorry drivers, dockers and power station employees crossing picket lines or handling coal. The strike was described as "one of the most aggressive trade union struggles since the 1926 General Strike", with some commentators even suggesting it was "the nearest the country had come to civil war for 400 years". Archbishop of Canterbury Robert Runcie accused Thatcher personally of fostering a "politics of confrontation", and blamed her policies for high unemployment, which he said had created "despair about the future". After a year out on strike, in March 1985, the NUM leadership conceded without a deal. The cost of the strike to the economy was estimated at least £1.5 billion. The strike was also blamed for much of the pound's fall against the US dollar. The government proceeded to close 25 unprofitable pits in 1985; by 1992, a total of 97 pits had been closed, with the remaining being sold off and privatised in 1994. These actions had great effect on the industrial and political complexion of the country. The eventual closure of 150 collieries, not all of which were losing money, resulted in a loss of tens of thousands of jobs and devastated entire communities, delivering a blow from which the coal industry, with 50 mines employing 6,000 people, has barely begun to recover, with plans for 58 new open-cast mines and up to a dozen new deep mines.

On the early morning of 12 October 1984, the day before her 59th birthday, Thatcher narrowly escaped injury in the Brighton hotel bombing carried out by the Provisional Irish Republican Army. Five people were killed in the attack, including the wife of Cabinet Minister John Wakeham; a prominent member of the Cabinet, Norman Tebbit, was injured, and his wife Margaret was left paralysed. Thatcher was staying at the hotel to attend the Conservative Party Conference, and insisted that the conference open on time the next day. She delivered her speech as planned in defiance of the bombers, a gesture which won widespread approval across the political spectrum, and measurably enhanced her personal popularity with the public. A Gallup poll that month found her personal approval rating up from 40% to 50%, and the Conservative lead over Labour widening from 1% to 12%.

Thatcher took office in the final decade of the Cold War, a period of strategic confrontation between the Western powers and the Soviet Union and its Warsaw Pact satellites. During her first year as prime minister she supported NATO's decision to deploy U.S. Cruise missiles and Pershing missiles in Western Europe. She permitted the United States to station more than 160 nuclear cruise missiles at Greenham Common, arousing mass protests by the Campaign for Nuclear Disarmament. Thatcher became closely aligned with the policies of U.S. President Ronald Reagan (1981–1989), and their closeness produced transatlantic cooperation. His policy of deterrence against the Soviets contrasted with the policy of détente which the West had pursued during the 1970s, and caused friction with allies who still adhered to the idea of détente. Thatcher was among the first Western leaders to respond warmly to reformist Soviet leader Mikhail Gorbachev. They met in London in 1984, three months before he became General Secretary. Thatcher declared that she liked him, and told Reagan, saying, "we can do business together". Following the Reagan-Gorbachev summit meetings from 1985 to 1988, as well as multiple reforms enacted by Gorbachev in the USSR, Thatcher declared in November 1988, "We're not in a Cold War now" but rather in a "new relationship much wider than the Cold War ever was." She continued, "I expect Mr Gorbachev to do everything he can to continue his reforms. We will support it." Thatcher initially opposed German reunification, telling Premier Gorbachev that "this would lead to a change to postwar borders, and we cannot allow that because such a development would undermine the stability of the whole international situation and could endanger our security." She expressed concern that a united Germany would align itself closer with the Soviet Union and move away from NATO. Recent records attribute Gorbachev as stating that "the West doesn’t want German reunification but wants to use us to prevent it", possibly because of the line taken by Thatcher and other European leaders such as France's Mr Mitterrand who was even thinking of a military alliance with Russia to stop it, "camouflaged as a joint use of armies to fight natural disasters". Thatcher's premiership outlasted the Cold War, which ended in 1989, and those who share her views on it credit her with a part in the West's victory, by both the deterrence and détente postures.

In March 1982 Thatcher approved the modernisation of the strategic nuclear force by ordering a new generation of Trident submarines to replace Polaris at a cost of £10 billion, creating 25,000 British jobs. She justified the expenditure on the basis that the United Kingdom was acquiring only the minimum deterrent against Soviet aggression and rejected participation in START negotiations unless the U.S. and Soviet arsenals were substantially reduced. She committed the government to using savings from co-operation with the United States in the nuclear field to strengthen British conventional forces.

On 19 December 1984, Thatcher and Deng Xiaoping of the People's Republic of China signed the Sino-British Joint Declaration, which committed Hong Kong to the status of a Special Administrative Region. Britain agreed to leave the region in 1997.

In April 1986 Thatcher, after expressing initial reservations, permitted U.S. F-111s to use RAF bases for the bombing of Libya in retaliation for the alleged Libyan bombing of a Berlin discothèque, citing the right of self-defence under Article 51 of the UN Charter. Thatcher told the House of Commons: "The United States has more than 330,000 forces in Europe to defend our liberty. Because they are there they are subject to terrorist attack. It is inconceivable that they should be refused the right to use American aircraft and American pilots in the inherent right of self-defence to defend their own people." The United Kingdom was the only nation to provide support and assistance for the U.S. action. Polls suggested that more than two out of three people disapproved of Thatcher's decision to accede to the U.S. request. Despite the Lebanon hostage crisis in in April 1986, the hijacking of Pan Am Flight 73 in September 1986, and the Lockerbie bombing in December 1988, Thatcher insisted that the raid had deterred further Libyan attacks. Thatcher also contended that her support for the U.S. bombing of Libya imposed an obligation on the United States to ratify a new extradition treaty with the United Kingdom in order to stand up to IRA violence. "What is the point", she asked, "of the United States taking a foremost part against terrorism and then not being as strict as they can against Irish terrorism, which afflicts one of their allies?" The U.S.-U.K. Supplementary Extradition Treaty, restricting the application of the political offence exception, signed in June 1986, and coming into force in December, was "hailed as a major improvement in the efforts of democratic nations to fight international terrorism".

Thatcher's preference for defence ties with the United States was also demonstrated in the Westland affair of 1986 when she acted with colleagues to allow the helicopter manufacturer Westland, a vital defence contractor, to refuse to link with the Italian firm Agusta in order for it to link with the management's preferred option, Sikorsky Aircraft Corporation of the United States. Defence Secretary Michael Heseltine, who had pushed the Agusta deal, resigned in protest after this, and remained an influential critic and potential leadership challenger.

In July 1986 Thatcher expressed her belief that economic sanctions against South Africa would be immoral because they would make thousands of black workers unemployed. Public dissatisfaction with her position grew steadily, reaching 65% in a MORI poll for The Times published in August 1986, following a boycott of the Commonwealth Games in Edinburgh by 32 nations. 49% of people surveyed said they would approve of an end to new investment by British companies, and a complete ban on trade, air or sporting links also failed to attract majority support. 46% said sanctions would not help bring an end to apartheid, while 44% said they would.

In 1986, in a controversial move, the Thatcher government abolished the Greater London Council, then led by the left-wing Ken Livingstone, as well as six Labour controlled metropolitan county councils. The government stated that they ordered this to decrease bureaucracy and increase efficiency, and encouraged transferring power to local councils for increased electoral accountability. Thatcher's opponents, however, held that the move was politically motivated, as the GLC had become a powerful centre of opposition to her government, and the county councils were in favour of higher local government taxes and public spending.

As Prime Minister, Thatcher met weekly with Queen Elizabeth II to discuss government business. She was just six months older than the Queen, and their relationship came under close scrutiny, with the media speculating that they did not get along overly well. While they displayed public images that largely contrasted, Tim Bell, a former Thatcher advisor, recalled, "Margaret has the deepest respect for the Queen and all her family". She was said to greet the Queen with a curtsey every time they met. In July 1986 sensational claims attributed to the Queen's advisers of a "rift" between Buckingham Palace and Downing Street "over a wide range of domestic and international issues" were reported by The Sunday Times. The immediate cause was said to be "the Queen's fear for the possible break-up of the Commonwealth" because of Thatcher's rejection of comprehensive sanctions against South Africa. Their relationship was characterised as "pragmatic and without any personal antagonism". The Palace issued an official denial, heading off speculation about a possible constitutional crisis. However a MORI poll for the Evening Standard suggested a sharp loss of support for the government following the controversy, giving Labour a six-point lead, reversing a previous Conservative six-point lead, while a separate MORI poll for The Times put Labour on 41% with a nine-point lead. After Thatcher's retirement a senior Palace source again dismissed as "nonsense" the "stereotyped idea" that she had not got along with the Queen or that they had fallen out over Thatcherite policies. Thatcher herself declared that "stories of clashes between 'two powerful women' were too good not to make up ... I always found the Queen's attitude towards the work of the Government absolutely correct".

At the time of the 1987 general election, Labour leader Neil Kinnock presided over a party deeply divided on policy agendas. Margaret Thatcher, in turn, led her party to victory, winning an unprecedented third term with a 102 seat majority, and became the longest continuously serving Prime Minister of the United Kingdom since Lord Liverpool (1812 to 1827), as well as the only Prime Minister of the 20th century to serve three terms. She was elected riding on an economic boom against a weak Labour opposition. The Conservatives won 42.2% of the popular vote, while the Labour party won 30.8% and Alliance won 22.6 %.

Thatcher, the former chemist, became publicly concerned with environmental issues in the late 1980s. In 1988, she made a major speech communicating the problems of global warming, ozone depletion and acid rain.

Thatcher introduced a new system for the government to raise revenue; she replaced local government taxes with a Community Charge or "Poll tax", in which property tax rates were made uniform, in that the same amount was charged to every individual resident, and the residential property tax was replaced with a head tax whose rate would be established by local governments. Thatcher's revolutionary system was introduced in Scotland in 1989 and in England and Wales the following year. A sceptical British public was disenchanted with Thatcher's system of local taxation and it was to be among the most unpopular policies of her premiership. What the Thatcher government did not anticipate was that local councils would raise their total shares from the taxes. As a result, the central Government capped rates that seemed out of line, resulting in charges of partisanship and the alienation of small-government Conservatives. The Prime Minister's popularity declined in 1989 as she continued to refuse to compromise on the tax. Unrest mounted and culminated in a number of riots, the most serious of which occurred at Trafalgar Square, London, on 31 March 1990; more than 100,000 protesters attended and more than 400 people were arrested. A BBC Radio poll in September 1989 indicated that almost three-quarters of the public were also against water privatisation. Despite public opposition to the poll tax and the privatisation of water, electricity, and British Rail, Thatcher remained confident that, as with her other major reforms, the initial public opposition would turn into support after implementation. A MORI poll for the Sunday Times in June 1988 found that more than 60% of voters agreed that in the long term the Thatcher government's policies would improve the state of the economy, while less than 30% disagreed; although income inequality had increased the poor were still better off than in 1979: 74% of Britons said they were satisfied with their present standard of living, while only 18% were dissatisfied.

At Bruges, Belgium, in 1988, Thatcher made a speech in which she outlined her opposition to proposals from the European Community, a forerunner to the European Union, for a federal structure and increasing centralisation of decision-making. Though she had supported British membership in the EC, Thatcher believed that the role of the organisation should be limited to ensuring free trade and effective competition, and feared that the EC approach to governing was at odds with her views of smaller government and deregulatory trends; in 1988, she remarked, "We have not successfully rolled back the frontiers of the state in Britain, only to see them re-imposed at a European level, with a European super-state exercising a new dominance from Brussels". A split was emerging over European policy inside the British Government and her Conservative Party. On 30 November 1988, when the European Court of Human Rights ruled that Britain's detention provisions were in breach of European law, the policy split extended to parliament with the presentation of a petition calling for a written British constitution. Thatcher reacted angrily to the ECHR ruling, and to the failure of Belgium and Ireland to extradite a suspected terrorist, Father Patrick Ryan, to face charges in Britain. She told the Commons: "We shall consider the judgment carefully and also the human rights of the victims and potential victims of terrorism." At a meeting before the Madrid European Community summit in June 1989, Chancellor of the Exchequer Nigel Lawson and Foreign Secretary Geoffrey Howe sought to persuade Thatcher to agree to circumstances under which Great Britain would join the Exchange Rate Mechanism, a preparation for monetary union, and abolish the pound as British currency. At the meeting, they both said they would resign if their demands were not met. Thatcher, as well as her economic advisor Alan Walters, was opposed to this notion and felt that the pound sterling should be able to float freely, and that membership would constrain the UK economy. Both Lawson and Howe eventually resigned and Thatcher remained firmly opposed to British membership in the European Monetary System.

Thatcher was challenged for the leadership of the Conservative Party by virtually unknown backbench MP Sir Anthony Meyer in the 1989 leadership election. Of the 374 Conservative MPs eligible to vote, 314 voted for Thatcher while 33 voted for Meyer; there were 27 abstentions. Thatcher noted, "I would like to say how very pleased I am with this result and how very pleased I am to have had the overwhelming support of my colleagues in the House and the people from the party in the country", while Meyer said he was delighted as well: "The total result I think is rather better than I had expected". Her supporters in the Party viewed the results as a success, and rejected suggestions that there was discontent within the Party.

Thatcher was visiting the United States when she received word that Iraqi leader Saddam Hussein had invaded neighbouring Kuwait. She met with US President George H. W. Bush, who had succeeded Ronald Reagan in 1989, during which Bush asked her, "Margaret, what is your view?" She recalled in an interview that she felt "that aggressors must be stopped, not only stopped, but they must be thrown out. An aggressor cannot gain from his aggression. He must be thrown out and really, by that time in my mind, I thought we ought to throw him out so decisively that he could never think of doing it again." She put pressure on Bush to deploy troops to the Middle East to drive the Iraqi army out of Kuwait. Bush was somewhat apprehensive about the plan, so Thatcher remarked to him during a telephone conversation, "This was no time to go wobbly!" Thatcher's government provided military forces to the international coalition in the Gulf War to pursue the ouster of Iraq from Kuwait.

Despite having the longest continuous period of office of any prime minister in the twentieth century, Thatcher had, on average during her premiership, the second-lowest approval rating of any post-war prime minister, at 40%, only beating Edward Heath; even after the Falklands War it had never risen above 55%; polls consistently showed that she was less popular than the Conservative party. A self-described conviction politician, Thatcher always insisted she did not care about her poll ratings, pointing instead to her unbeaten election record. Moreover, in relative terms, Thatcher's personal position had remained consistently strong: a Marplan poll for the Sunday Express in October 1988 showed that Thatcher was still trusted by 61% of Britons to lead the country, compared with only 17% for Labour leader Neil Kinnock. Thatcher's capacity to lead was trusted by 87% of Conservative voters and 46% of Labour voters. A Telephone Surveys poll for the Sunday Express in September 1990, during the Gulf crisis, found that 65% of voters preferred Thatcher as a crisis leader to Kinnock, who polled 20%. A Mori poll for the Sunday Times in September 1989 showed that Thatcher was still the public's preferred choice of Conservative leader, attracting the support of 32% of voters, her pro-European former cabinet colleague Michael Heseltine coming second on 22%. However, by March 1990, in the face of rising inflation and the threat of a recession and inevitable mass unemployment, Thatcher's support had halved to 15%, with Heseltine's doubling to 40%. Opposition to the poll tax and the divisions opening in the parliamentary party over European integration left Thatcher increasingly vulnerable to a challenge.

By November 1990 the Conservatives had been trailing Labour for 18 months. Although a Mori survey for the Sunday Times showed that 83% of Conservative voters were satisfied by the way Thatcher represented the United Kingdom in Europe, a BBC poll found that Labour had increased its lead by 5 points to 14%, its biggest lead since May, while a poll for the Evening Standard found that Labour had nearly doubled its lead over the Conservatives to 13.2 points. Low poll ratings, along with Thatcher's combative personality and willingness to override colleagues' opinions, contributed to discontent in the parliamentary party. On 1 November 1990, Geoffrey Howe, for 15 years one of Thatcher's most "loyal and self-effacing" supporters, resigned from his position as Deputy Prime Minister over her refusal to agree to a timetable for British membership of the single currency. In his resignation speech in the Commons on 13 November, referring to Thatcher's promise to veto any arrangement which jeopardised the pound sterling, Howe famously complained: "It is rather like sending your opening batsmen to the crease only for them to find the moment that the first balls are bowled that their bats have been broken before the game by the team captain." Howe's resignation put Thatcher's future in doubt, and was afterwards recognised as dealing a "fatal blow" to her premiership. While 59% of the British public polled for The Independent by Number Market Research agreed with Thatcher's opposition to monetary union, 64% still felt she ought to retire. A few days later Heseltine challenged her for the leadership of the party. A Gallup poll for the Daily Telegraph showed that 28% of voters would be more inclined to vote Conservative if Heseltine were leader, and only 7% would be less inclined. Five separate polls indicated that he would give the Conservatives a national lead over Labour. Heseltine attracted sufficient support from the parliamentary party in the first round of voting to prolong the contest to a second ballot. Although Thatcher initially stated that she intended to contest the second ballot, she consulted with her Cabinet and decided to withdraw from the contest. Thatcher said that pressure from her colleagues helped her to conclude that the unity of the Conservative Party and the prospect of victory in the next general election would be more likely if she resigned. Early on the morning of 22 November, the 65-year-old Prime Minister announced to the Cabinet that she would not be a candidate in the second ballot. Thatcher informed the Queen of her decision, and a statement was released from 10 Downing Street at 09.34:

The Prime Minister, the Rt. Hon. Margaret Thatcher, F.R.S., has informed the Queen that she does not intend to contest the second ballot of the election for leadership of the Conservative Party and intends to resign as Prime Minister as soon as a new leader of the Conservative Party has been elected… "Having consulted widely among my colleagues, I have concluded that the unity of the Party and the prospects of victory in a General Election would be better served if I stood down to enable Cabinet colleagues to enter the ballot for the leadership. I should like to thank all those in Cabinet and outside who have given me such dedicated support."

Some sections of the British public were stunned, but there were also scenes of rejoicing at the news. After visiting the Queen at Buckingham Palace, she later arrived at the House of Commons to a debate; Neil Kinnock, Leader of the Opposition, proposed a motion of no confidence in the government, and Thatcher displayed her combativeness. She said:

Eleven years ago we rescued Britain from the parlous state to which socialism had brought it. Once again Britain stands tall in the councils of Europe and of the world. Over the last decade, we have given power back to the people on an unprecedented scale. We have given back control to people over their own lives and over their livelihoods, over the decisions that matter most to them and their families. We have done it by curbing the monopoly power of trade unions to control, even victimize the individual worker.