Baroness Margaret Thatcher character jug modeled by Ray Noble and produced by Noble Ceramics of Hayling Island, England, in a limited edition of 1,000 in 1995. Margaret Hilda Thatcher (1925-2013) was Prime Minister of the United Kingdom from 1979 to 1990 and Leader of the Conservative Party from 1975 to 1990. She was the first female British prime minister and the longest-serving British prime minister of the 20th century. As prime minister, she implemented economic policies that became known as Thatcherism. A Soviet journalist dubbed her the "Iron Lady", a nickname that became associated with her uncompromising politics and leadership style.