Harold Adrian Russell “Kim” Philby (1 January 1912 – 11 May 1988) was a high-ranking member of British intelligence who worked as a double agent before defecting to the Soviet Union in 1963. He served as both an NKVD and KGB operative.
In 1963, Philby was revealed to be a member of the spy ring now known as the Cambridge Five, the other members of which were Donald Maclean, Guy Burgess, Anthony Blunt and, possibly, John Cairncross. Of the five, Philby is believed to have been most successful in providing secret information to the Soviet Union. His activities were moderated only by Joseph Stalin’s fears that he was secretly on Britain’s side. Philby was an Officer of the Order of the British Empire (OBE) from 1946 to 1965. (Source: Wikipedia)
Look out for bias on Wikipedia, especially concerning what in the West are considered controversial figures or ideas. Try reading Kim Philby’s autobiography, “My Silent War“, to get the full story. – PC