Margaret Hilda Thatcher, the Rt Hon. Baroness Thatcher, LG OM PC FRS (née Roberts): Born: October 13, 1925. Died: April 8, 2013. Prime Minister of Britain: 1979–1990. Margaret Thatcher was without doubt one of the most remarkable individuals of the 20th century. She made history by becoming Britain’s first woman prime minister and winning three consecutive general elections, making her the longest-serving British PM in the 20th century. At the same time she was one of the m…