David John Moore Cornwell (born 19 October 1931), known by the pseudonym John le Carré ( ), is a British author of espionage novels. During the 1950s and the 1960s, he worked for both the Security Service and the Secret Intelligence Service, and began writing novels under his pen name. His third novel, "The Spy Who Came in from the Cold" (1963), became an international best-seller and remains one of his best-known works. Following the success of this novel, he left MI6 to become a full-time author.