A 70-year-old retired physicist who lives in Cambridge may have been the long-suspected American spy inside the Los Alamos nuclear research centre, who kept the Soviet Union abreast of America's development of the atom bomb in 1944 and 1945.
The Washington Post yesterday identified the man as Theodore Alvin Hall, resident in England since 1962, but who was recruited as an exceptionally promising 19-year old Harvard physics student to join the Manhattan Project that culminated with the first atomic explosion in the New Mexico desert on 16 July, 1945.
Basing its case on recently declassified Soviet and US intelligence documents, the Post says Mr Hall was identified as an agent by the FBI in the early 1950s after evidence emerged that Manhattan had been penetrated by Moscow. He was identified by name in a KGB message of November 1944 which the Americans later decoded during the Venona decryption project that would unearth the British diplomat, Donald McLean, as a spy. None the less, US security apparently did not try to prevent him from leaving the country.
Contacted by the Post, Mr Hall neither confirmed nor denied the accusation. "That is precisely the kind of question I do not want to get dragged into right now," he said.
Soviet documents suggest the KGB was running two key agents inside Los Alamos, one code-named "Charles" and identified as Klaus Fuchs, who was arrested in Britain in 1950. The other was called "Mlad" (Russian for ''young man''). Circumstantial evidence, much of it in other decoded Venona messages, suggests that Mlad was Mr Hall.
Many of the scientists at Los Alamos, including their leader, Robert Oppenheimer, and the Italian physicist, Enrico Fermi, been accused of helping the Soviet Union acquire US atom secretsand thus allowing Stalin to build his own bomb by 1948, far earlier than would otherwise have been the case.
Now evidence points to Mr Hall. One of the couriers who carried his information was Leontine (Lona) Cohen, wife of the Soviet agent Morris Cohen. As British citizens, under the aliases of Peter and Helen Kroger, they were arrested in London in 1961 and jailed for their role in the Portland spy ring before being returned to Russia in a 1969 spy swap.