At the Quebec Conference in August 1943, the Prime Minister of the United Kingdom, Winston Churchill, and the President of the United States, Franklin Roosevelt, signed the Quebec Agreement, which merged Tube Alloys with the American Manhattan Project to create a combined British, American and Canadian project. The British contribution to the Manhattan Project included assistance in the development of gaseous diffusion technology at the SAM Laboratories in New York, and the electromagnetic separation process at the Berkeley Radiation Laboratory. John Cockcroft became the director of the joint British-Canadian Montreal Laboratory. A British mission to the Los Alamos Laboratory led by James Chadwick, and later Peierls, included scientists such as Geoffrey Taylor, James Tuck, Niels Bohr, William Penney, Frisch, Ernest Titterton, and Klaus Fuchs, who was later revealed to be a spy for the Soviet Union. As overall head of the British Mission, Chadwick forged a close and successful partnership with Brigadier General Leslie R. Groves, the director of the Manhattan Project, and ensured that British participation was complete and wholehearted.