In 1942, he began working on the British effort to build an atomic bomb (codenamed Tube Alloys) at the Cavendish Laboratory.

By 1944, Tube Alloys had been merged with the American Manhattan Project and he was sent to Los Alamos.

That fall, he contacted the Soviet Embassy in London, and volunteered to supply reports on his own work at Tube Alloys.

He moved to Trinity College, Cambridge in 1940 to work on Tube Alloys, the wartime atomic energy project.

It is unlikely that Canadian officials were aware of the Manhattan Project beyond the circumstances of the delivery of "Tube Alloys".

"we will not either of us communicate any information about Tube Alloys to third parties except by mutual consent"

In the Second World War, atomic research also took place on the site, under the codename Tube Alloys, whereby uranium hexafluoride had been made.

Both then moved into the secret team that would design a British atomic bomb, and they ran the key committees of Tube Alloys, as it was called.

In early 1941, he was invited by the British physicists to participate in Tube Alloys, the secret and classified British development of nuclear weapons.

Along the way, the project absorbed its earlier British counterpart, Tube Alloys.