"Kim Philby was the greatest spy in history, a brilliant and charming man who rose to head Britain's counterintelligence against the Soviet Union during the height of the Cold War - while he was secretly working for the enemy. And nobody thought he knew Philby like Nicholas Elliott, Philby's best friend and fellow officer in MI6. The two men had gone to the same schools, belonged to the same exclusive clubs, grown close through the crucible of wartime...