Web Of Lies
Despite growing suspicions, British intelligence couldn't pin Philby down. In 1951, Philby was called to London. He was questioned harshly but never formally charged. The evidence was thin, and his charm disarmed even seasoned investigators.
One MI5 officer described him as "more of an enigma than ever." Even a confession from Klaus Fuchs, the man who leaked atomic bomb secrets to the Soviets, didn't lead to action against Philby.