When we think of spies, we often picture Ian Flemming’s James Bond or films like “Mission Impossible.” In reality, being a Cold War spy requires a less noticeable approach, which is exactly how the Cambridge Five went about their espionage. The five men began by securing important jobs in the British government, with Kim Philby and Guy Burgess managing to join the U.K.’s Security Intelligence Service, or MI6 (per BBC).

According to Historic Mysteries, these spies transferred classified information to the Soviet Union from the end of World War II up until the Cold War. The double agents flew under the radar until 1951 when Burgess and MacLean defected to Russia over fears they had been discovered (per BBC).

Philby came under suspicion in 1955, but was not arrested due to lack of evidence, as Historic Mysteries notes. Eventually, evidence came to light that outed Philby, but in 1963 he also fled to Russia, where he lived until his death. Blunt came under suspicion in 1964 and confessed to his crimes after being interrogated. Cairncross actually confessed during a meeting with MI6 in 1964, but it was kept under wraps until 1979 when he confessed his crimes again to a journalist (per Historic Mysteries).