Premiership of Margaret Thatcher Premiership of Margaret Thatcher Margaret Thatcher served as Prime Minister of the United Kingdom from May 1979 to November 1990. She became Prime Minister after serving as Leader of the Conservative Party since 1975. In domestic affairs, Thatcher is best known for her sweeping policies concerning the affairs of the economy, including the privatisation of most nationalised industries. In foreign policy, she fought a war against Argentina and played a key role with President Ronald Reagan and Soviet leader Mikhail Gorbachev in ending the Cold War. By the late 1980s, she was alienating many senior members of her Cabinet by
Third Thatcher ministry European Community. On 14 November, former cabinet minister Michael Heseltine challenged Thatcher's leadership. Thatcher polled higher than him in the first round of the leadership contest, but failed to gain an outright victory in the first round of voting. Within minutes of the result being announced, Thatcher informed reporters that she intended to let her name go forward for the second ballot. However, on 22 November, before a second round of the contest could take place, Margaret Thatcher announced her resignation as Prime Minister and Leader of the Conservative Party after more than 11 years, explaining that she was resigning