7. The Venona Project revealed contacts between the British Embassy in Washington and Soviet agents
In the late 1940s, the analysts at Arlington Hall involved in the Venona Project revealed the level of espionage by the Soviets regarding the Manhattan Project. It also revealed messages which described documents being sent from the British Embassy in Washington via a code-named courier to Soviet agents in New York, whence to Moscow. The analysts at Arlington Hall hesitated over presenting the information, uncertain over which American intelligence organization to approach. The newly formed CIA presented one option, the FBI another, and Army Intelligence yet another. While they hesitated Kim Philby became aware of the situation. Philby knew the courier had been Donald Maclean, then in England. He had little confidence Maclean would stand up to interrogation without revealing the Cambridge spies.
Philby was in Washington in the official position of First Secretary to the British Embassy. He also held the position of senior officer of British Intelligence, and the mandate to effect cooperative efforts with the American CIA. When Burgess arrived in Washington as Second Secretary, he took up residence in Philby’s household. Burgess continued to indulge in his penchant for excessive drink. He avoided arrests for drunken driving and speeding by using diplomatic immunity, and in general treated American laws and American people with contempt. Yet, to Philby, Burgess offered a possible means of warning Maclean that the Americans were closing in on his espionage activities. Philby knew that if Maclean were subject to arrest the activities of all of the Cambridge 5 were liable to exposure. To prevent it he devised a plan to rid himself of the insufferable Burgess and warn Maclean at the same time.