Bill Haydon

Bill Haydon is a fictional character created by John le Carré who features in le Carré's 1974 novel Tinker Tailor Soldier Spy. He is a senior officer in the British Secret Intelligence Service who serves as a Soviet mole. The novel follows aging spymaster George Smiley's endeavours to uncover the mole.

The character is partly modelled after the real-life double agent Kim Philby, part of the notorious Cambridge Five spy ring in Britain, who defected to the USSR in 1963.