Born in British India, Philby was educated at Westminster School and Trinity College, Cambridge. He was recruited by Soviet intelligence in 1934. After leaving Cambridge, Philby worked as a journalist, covering the Spanish Civil War and the Battle of France. In 1940 he began working for the United Kingdom's Secret Intelligence Service (SIS or MI6). By the end of the Second World War he had become a high-ranking member. In 1949 Philby was appointed first secretary to the British Embassy in Washington and served as chief British liaison with American intelligence agencies. During his career as an intelligence officer, he passed large amounts of intelligence to the Soviet Union, including a plot to subvert the communist regime of Albania.
Philby was suspected of tipping off two other spies under suspicion of Soviet espionage, Donald Maclean and Guy Burgess, both of whom subsequently fled to Moscow in May 1951. Philby resigned from MI6 in July 1951. He was publicly exonerated in 1955, after which he resumed his career as both a journalist and a spy for SIS in Beirut, Lebanon. In January 1963, having finally been unmasked as a Soviet agent, Philby defected to Moscow, where he lived until his death in 1988.