Margaret Hilda Thatcher, Baroness Thatcher, was Prime Minister of the United Kingdom from 1979 to 1990 and Leader of the Conservative Party from 1975 to 1990. The longest-serving British prime minister of the 20th century, she was the first woman to hold that office. A Soviet journalist dubbed her the "Iron Lady", a nickname that became associated with her uncompromising politics and leadership style. As prime minister, she implemented policies that became known as Thatcherism. Thatcher studied chemistry at Somerville College, Oxford, and worked briefly as a research chemist, before becoming a barrister. She was elected Member of Parliament for Finchley in 1959. Edward Heath appointed her Secretary of State for Education and Science in his 1970–1974 government. In 1975, she defeated Heath in the Conservative Party leadership election to become Leader of the Opposition, the first woman to lead a major political party in the United Kingdom.