Guy Burgess and Donald Maclean

Two members of the so-called " Cambridge spy ring" -- a circle of communist sympathizers at the Cambridge University who were recruited by the KGB in the 1930s. Burgess and Maclean joined the British Foreign Office and began supplying secret information to the Soviets. Maclean was particularly damaging: from a Foreign Office post in Washington he turned over highly classified nuclear information and secrets relating to the formation of NATO. Burgess, meanwhile, became a member of the British Secret Intelligence Service (MI-6).

In May 1951, fellow Soviet double-agent Kim Philby warned them that Allied counter-intelligence suspected Maclean was a mole. Burgess and Maclean mysteriously vanished and were not heard from again until they surfaced in the Soviet Union in 1956. Both men lived out the rest of their lives there, by varying degrees alcoholic and disillusioned.