By May 1947 Gardner had read a decrypt that implied the Soviets ran an agent with access to sensitive information from the War Department General Staff, U.S. Army Air Corps Major William Ludwig Ullmann.

Checking the message against a complete copy of the telegram provided by the British Embassy, the cryptanalysts confirmed beyond doubt that during the war the Soviets had a spy who had access to secret communication between the president of the United States and the prime minister of Britain.

[6] Peter Wright met Meredith Gardner in London after the arrests of the atom spies: "He was a quiet, scholarly man, entirely unaware of the awe in which he was held by other cryptanalysts.

He used to tell me how he worked on the matches in his office, and of how a young pipe-smoking Englishman named Philby used to regularly visit him and peer over his shoulder and admire the progress he was making.

Wright added that Gardner "was appalled at the fact that his discovery had led, almost inevitably, to the electric chair, and felt (as I did) that the Rosenbergs, while guilty, ought to have been given clemency.