Harold Adrian Russell (Kim) Philby was a senior officer in the British Secret Intelligence Service (SIS) for ten years, but was actually an agent of the Soviet KGB. This gives him a claim to have been one of the most successful spies in the history of espionage.

Philby was the son of the famous Arabist St John Philby, and was born in India, where his father was serving as a magistrate. He was nicknamed Kim, after the hero of Kipling's novel, when he began speaking Punjabi before English. He was recruited to the KGB while still a student at Cambridge, and along with other KGB recruits - Donald Maclean, Guy Burgess, Anthony Blunt - from the same university, eventually became infamous as a member of 'the Cambridge spy ring'. they were All secret supporters of the Communist Party.

To provide a cover, Philby began openly expressed right-wing opinions. Philby and Guy Burgess joined the Anglo-German Fellowship, a pro-Nazi pressure group. Philby got himself appointed as a reporter with The Times and on the outbreak of the Spanish Civil War he was sent to Spain. Over the next couple of years he provided articles that were very sympathetic to General Francisco Franco and the Nationalist Army. Franco was grateful for the support Philby gave to the Nationalists and on 2nd March, 1938, awarded him the Red Cross of Military Merit. These reports convinced those on the right-wing of British politics that Philby had abandoned his former political views.philby rose to be the SIS's liaison officer in Washington with the CIA and the FBI, before he fell under suspicion in 1951 and was recalled to London. There he successfully resisted interrogation. When the SIS refused to reinstate him, he went to the Lebanon as a freelance intelligence agent, under cover as a journalist.

In 1963 testimony from a Soviet defector clinched the case against Philby, and a fellow SIS officer went to Beirut to persuade him to confess to his work for the KGB. Instead, Philby boarded a Soviet freighter and fled to Moscow. There he had a miserable time at first, because the KGB was uncertain whether he was a British intelligence plant.

He was rehabilitated in the early 1980s, became a consultant to the KGB, lectured to young KGB officers and received various Soviet awards and honours. He wrote 'My Silent War', an account of his life as a KGB penetration agent, and appeared on Soviet television in a programme honouring the British author Graham Greene, his former wartime colleague in the SIS.

In 1988 Philby consented to a week-long interview with The Sunday Times, in which he justified his treachery to his native country by saying that when he made his commitment to the KGB, he believed that the western democracies were too weak to resist the rise of Fascism in Europe and that only the Soviet Union would be able to defeat it.

The release of KGB files after the end of the Cold War cast doubt on Philby's value to Moscow during the years he worked for the Soviet Union. It appeared that many senior KGB officers had discounted his information, arguing that it was 'too good to be true'. Philby never knew any of this because he died, happy and content with his fourth wife, a Russian, Rufina Pukhova, before the collapse of the Communist regime he loved.

He died in 1988 and was given a hero's funeral by the Soviet government.

Tim Powers based the book 'Declare' on his unusual life story, providing a supernatural explanation for his behavior.