An Original No10 Downing Street Unused Bookplate Paper Signed by Prime Minister Margaret Thatcher C1980. Margaret Hilda Thatcher, Baroness Thatcher, 1925-2013, 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. As prime minister, she implemented 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. Size is 130mm x 90mm. Condition is good.