Harold Adrian Russell "Kim" Philby was a British intelligence officer and a spy for the Soviet Union. In 1963, he was revealed to be a member of the Cambridge Five, a spy ring which had divulged British secrets to the Soviets during World War II and in the early stages of the Cold War. Of the five, Philby is believed to have been the most successful in providing secret information to the Soviets.

Edith Tudor-Hart was an Austrian-British photographer and spy for the Soviet Union. Brought up in a family of socialists, she trained in photography at Walter Gropius's Bauhaus in Dessau, and carried her political ideals through her art. Through her connections with Arnold Deutsch, Tudor-Hart was instrumental in the recruiting of the Cambridge Spy ring which damaged British intelligence from World War II until the security services discovered all their identities by the mid-1960s. She recommended Litzi Friedmann and Kim Philby for recruitment by the KGB and acted as an intermediary for Anthony Blunt and Bob Stewart when the rezidentura at the Soviet Embassy in London suspended its operations in February 1940.