This is the story of the deadliest double agent in history and how he deceived and destroyed my own uncle, James Angleton, who ran Counterintelligence in the CIA for 20 years. The double agent was a man named Kim Philby. Philby was a major MI6 operative at the same time he was on the payroll of the KGB. In World War II, Philby taught Angleton the spy craft trade. After the war, he duped Angleton into giving him access to CIA and FBI files, which he then passed to the KGB. It destroyed Angleton.