Cambridge Five spy ring exposed

On May 25, 1951, two officials of the British Foreign Office, Guy Burgess and Donald Maclean, left England by ferry and disappeared. They surfaced in Moscow in 1956. Maclean was about to be interrogated as the suspected source of leaks identified by American codebreakers, and someone had warned him. Suspicion quickly fell on Kim Philby, a rising officer in MI6, Britain's foreign intelligence service, who had been posted to Washington as liaison with the CIA and FBI and was a friend of Burgess. Philby was forced out of MI6 but publicly cleared in 1955, and he defected to Moscow from Beirut in January 1963.¹³

All five had been recruited by Soviet intelligence in the 1930s, when they were students or young graduates at Cambridge University. They were drawn to communism by the Depression and the rise of fascism, and they pursued careers in the institutions that held Britain's secrets. Maclean passed information on atomic cooperation and Western strategy; Philby betrayed agents and operations, including Western attempts to infiltrate Albania; John Cairncross passed on decrypts from Bletchley Park during World War II; and the art historian Anthony Blunt, surveyor of the king's pictures, worked in MI5 during the war.¹²³

Blunt confessed secretly in 1964 in exchange for immunity, and was publicly named by Prime Minister Margaret Thatcher in 1979. Cairncross was widely identified as the fifth man in 1990. The scandal damaged British intelligence's standing in Washington for years, and its class dimension, upper-middle-class men protected by their own networks, became part of the story. MI5 files released in 2015 and later show how long suspicions went unacted on.¹²³