31 Mar Kim Philby, the most successful of the Cambridge spies, tried to drink himself to death in Moscow because he was disillusioned with communism and tortured for the Times, and in joined the Secret Intelligence Service (SIS, or MI6), becoming a double agent and passing many secrets to the Kremlin. 30 Mar Despite knowledge of the the report reaching the highest levels of US intelligence services and government, it was not independently verified. But insider sources told the BBC Mr Kalugin had been identified as a spy and was being monitored prior to his return to Russia in August – separately from Mr . An agent who pays spies and bribes authorities A person sent by the intelligence agency of his or her own country who approaches an intelligence agency in the hope of being recruited as a spy so as to allow a double agent operation for Escort. The operations officer assigned to lead a defector along an escape route.