KLAUS FUCHS: ATOM BOMB SPY
Harwell was literally being constructed from scratch. When he arrived, he found that Perrin and his superiors had built an austere village in the English countryside. There were several laboratories and a number of barracks-like housing units for the staff. Trees had been bulldozed, and the area was muddy and barren. Still, Klaus looked forward to being at Harwell, to returning to his work.
The next three years were happy ones. He was the assistant director. The work went well. He had friends. He felt fulfilled.
He continued to provide information to his new Russian contact, but the secrets were really no longer secret. They were, in effect, redundant. By the end of 1947, Klaus had virtually ended his contact with the Russians, and they, in turn, were no longer eager to keep Klaus among their spies.
One evening in late November 1949, at a party being held at Henry Arnold's house, a merry gathering of the Harwell group of scientists, Klaus drew his host aside. Henry Arnold had become a good friend, even in his problematic position as director of security for Harwell. Klaus explained to his friend that he had a problem. Klaus was contemplating whether he should resign from Harwell, he told Arnold.
Arnold pricked up his ears. He had been alerted by MI6 that Klaus might be the suspected British nuclear scientist who had been mentioned in the decoded Venona intercepts. The Americans had finally solved the Soviet code, and now, more than three years after the fact, a combined effort of the United States Army and the FBI had decoded messages from 1943 to 1945 that Russian agents had transmitted to Moscow, and return messages from KGB Headquarters. Unknown to Klaus, Arnold had been observing him for a number of weeks.
Fuchs explained that his father had accepted a professorship in East Germany, and that he wondered whether that might compromise his security clearance. Arnold said he did not think it would be a problem, but suggested that Fuchs speak to William Skardon, who was with M15 and might know about such things.