Alec Douglas-Home

Alexander Frederick Douglas-Home, Baron Home of the Hirsel, known as Lord Dunglass from 1918 to 1951 and the Earl of Home from 1951 to 1963, was a British statesman and Conservative politician who served as Prime Minister of the United Kingdom from 1963 to 1964. He was the last prime minister to hold office while being a member of the House of Lords, before renouncing his peerage and taking up a seat in the House of Commons for the remainder of his premiership. His reputation, however, rests more on his seven years over two stints as Foreign Secretary than on his brief premiership.

— Source: Wikipedia (CC-BY-SA).