British politician Baroness Margaret Hilda Thatcher from 1979 served; measures against inflation, a brief war in the Falkland Islands in 1982, and the passage of a poll tax marked her prime administration to 1990.

Margaret Hilda Thatcher, Thatcher, LG, OM, PC, FRS (née Roberts) of the United Kingdom from 1979 to 1990 and Leader of the Conservative Party from 1975 to 1990. She was the first and to date only woman to hold either post.

She went to read chemistry at Somerville College, Oxford. She was selected as Conservative candidate for Finchley in 1958 and took her seat in the House of Commons in the following year of 1959. Upon the election of Edward Heath in 1970, people appointed Thatcher as secretary of state for education and science. In 1974, she backed Sir Keith Joseph for the Conservative party leader, but he fell short and afterward dropped out the race. Thatcher entered and led the Conservative party in 1975. She defiantly opposed the Soviet Union, and her tough-talking rhetoric gained her the nickname the "iron lady." As the Conservative party maintained leads, Thatcher went in the general election of 1979.

The longest tenure of Thatcher the longest since that of Lord Salisbury and was the longest continuous period in office since the tenure of Lord Liverpool in the early 19th century. This first woman led a major party in the United Kingdom and held any of the four great offices of state. After her resignation, she was ennobled as Thatcher, of Kesteven in the County of Lincolnshire, which entitled her to sit in the House of Lords. During her tenure, she needed sleep of just four hours in a night.