Anthony Blunt

Anthony Frederick Blunt (26 September 1907 – 26 March 1983), styled Sir Anthony Blunt KCVO from 1956 to 1979, was a British art historian and spy. In 1964, he confessed to having been a spy for the Soviet Union and was part of the spy group the Cambridge Five.
Blunt was the "fourth man" of the Cambridge Five, a group of Cambridge-educated spies working for the Soviet Union from some time in the 1930s to at least the early 1950s. 
The height of his spying was during World War II, when he passed intelligence to the Soviet Union. His confession was a closely guarded secret for years. It was revealed by Prime Minister Margaret Thatcher in November 1979. He was stripped of his knighthood immediately.
Blunt was professor of art history at the University of London, director of the Courtauld Institute of Art, and Surveyor of the Queen's Pictures.