Klaus Fuchs wasn’t the only spy to escape the notice of the British intelligence services

Kim Philby, who may or may not have tipped off Fuchs about British intelligence placing him under surveillance, himself lived a double life as a notorious spy. One of the infamous Cambridge Five, he was recruited by the Soviet Union as early as 1934, before he had even begun working for British intelligence. Alongside Philby, Guy Burgess, Donald Maclean, Anthony Blunt and John Cairncross formed the other members of the ring. Among the intelligence Philby himself was able to give to the Soviet Union was information about an Anglo-american plot to subvert the communist regime in Albania. In 1951, following the defections of Burgess and Maclean, suspicion fell upon Philby. However, in 1955 he was publicly exonerated and able to resume his career as a journalist, although he had been forced to leave MI6. But the writing was on the wall and a mere eight years later he was finally unmasked as a spy, after which he defected to Russia. He spent the rest of his life virtually under house arrest in Moscow and occupied his time writing his memoirs until his death in 1988.