7. Kim Philby and the Cambridge Five
Kim Philby, a British intelligence officer, led a double life as a Soviet spy, becoming the most notorious member of the Cambridge Five—a group of British spies who passed information to the Soviet Union during and after World War II. Recruited by Soviet intelligence in 1934, Philby infiltrated MI6, rising to a senior position while secretly providing the KGB with sensitive information. His espionage activities significantly compromised Western intelligence operations during the Cold War. In 1963, facing mounting suspicion, Philby defected to the Soviet Union, where he was honored as a hero. Declassified MI5 files released in 2025 revealed details of his recruitment and espionage activities (usnews.com).
