He was also responsible for tipping off two other spies under suspicion of espionage, Donald Maclean and Guy Burgess, both of whom subsequently fled to Moscow in May 1951. The defections of Maclean and Burgess cast suspicion over Philby, resulting in his resignation from MI6 in July 1951.

What happened to Burgess and Maclean?

Maclean was in the Foreign Office during the same period. In 1951, tipped off by Philby that they were under suspicion, Burgess and Maclean defected to the Soviet Union, where they spent the rest of their lives.

Who is considered the biggest mole in British intelligence?

Harold Adrian Russell "Kim" Philby (1 January 1912 – 11 May 1988) was a high-ranking member of British intelligence who worked as a double agent before defecting to the Soviet Union in 1963. He served as both an NKVD and KGB operative.