John le Carré (A.K.A. David John Moore Cornwell) worked forMI5 and MI6 in the 1950s and 1960s, before leaving the secret service to devote himself to writing after the success of The Spy Who Came In from the Cold. Cornwell wrote under his pseudonym of John le Carré because it was not acceptable for members of the Foreign Office to publish under their own names. John is Le Carré's second forename, whilst the words "le carré" mean "the square" in French.
In 1950 le Carré joined the British Army's Intelligence Corps in Austria, where his German proved useful in interrogating people who had fled westward across the Iron Curtain. In 1952 he returned to England to study at Lincoln College, Oxford where he carried out secret assignments for MI5, which included joining far-left groups in order to collect information about possible Soviet agents.
His work was affected by Kim Philby, a British double agent (one of the Cambridge Five), who blew the cover of dozens of British agents to the KGB, David Cornwell among them. Years later, le Carré carefully depicted and analysed Philby's weakness and deceit in the guise of "Gerald" the mole, who is hunted by George Smiley in the central novel of le Carré's work, Tinker, Tailor, Soldier, Spy.