Guy Francis de Moncy Burgess was a British diplomat and Soviet double agent, and a member of the Cambridge Five spy ring that operated from the mid-1930s to the early years of the Cold War era. His defection in 1951 to the Soviet Union, with his fellow spy Donald Maclean, led to a serious breach in Anglo-United States intelligence co-operation, and caused long-lasting disruption and demoralisation in Britain's foreign and diplomatic services.

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.