The Cambridge Five was a ring of spies in the United Kingdom that passed information to the Soviet Union during the Second World War and the Cold War and was active from the 1930s until at least the early 1950s. None of the known members were ever prosecuted for spying. The number and membership of the ring emerged slowly, from the 1950s onwards.

Donald Duart Maclean was a British diplomat and Soviet double agent who participated in the Cambridge Five spy ring. After being recruited by a Soviet agent as an undergraduate student, Maclean entered the civil service. In 1938, he was appointed as Third Secretary at the British embassy in Paris. He served in London and Washington, D.C., achieving promotion to First Secretary. He was subsequently posted to Egypt, and then was appointed head of the American Department in the Foreign Office.