Margaret Hilda Thatcher, Baroness Thatcher (née Roberts; 13 October 1925 – 8 April 2013), 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.