Bill Haydon is a fictional character created by John le Carré in le Carré's Tinker Tailor Soldier Spy.
Haydon was born around 1917; no specific year is given but he is known to have been an undergraduate at Oxford University in 1937. He comes from an aristocratic family with connections throughout British high society. A polymath of sorts with a brilliant and charming personality, he excels as a student, takes up remote languages with ease, and proves a gifted painter while at Oxford. He is identified for recruitment in the Circus (John le Carré's lightly fictionalised version of MI6/SIS) by his tutor and acts in turn as a talent-spotter among his classmates, most noticeably Jim Prideaux with whom he forms an enduring friendship and possibly a homosexual relationship. In World War II, Haydon builds a superb record in Nazi-occupied Europe and the Middle East, such that he elicits comparisons with Lawrence of Arabia. Unbeknownst to the British, Haydon is also recruited as a Soviet agent around that time by Karla, Moscow Centre's crafty and legendary spymaster.
After the war, Haydon holds positions of increasing importance in the Circus, becomes its premier expert on the Soviet Union, and eventually rises to the senior staff of Control, the unnamed Chief of the Circus. In the early years of the Cold War, he limits his espionage activities to 'selected gifts of intelligence' that advance the Soviet cause over the American one without harming British interests. The Suez crisis of 1956 convinces him that Britain has lost all influence as a world power and leads him to become a 'full-fledged Soviet mole with no holds barred.' In 1961, he formally receives Soviet citizenship, then achieves the rank of Soviet intelligence colonel and is awarded further Soviet decorations over the next ten years.