now known as the Chalk River Laboratories. Britain and Canada agreed to pay the cost of this project, but the United States had to supply the heavy water. Because it was unlikely to have any impact on the war, Conant in particular was cool about the proposal, but heavy water reactors were still of great interest. Groves was willing to support the effort and supply the heavy water required, but with certain restrictions. The Montreal Laboratory would have access to data from the Metallurgical Laboratory's research reactors at Argonne and the X-10 Graphite Reactor at Oak Ridge, but not from the production reactors at the Hanford Site; nor would they be given any information about the chemistry of plutonium, or of methods for separating it from other elements. This arrangement was formally approved by the Combined Policy Committee meeting on 19 September 1944. Chadwick supported the British contribution to the Manhattan Project to the fullest extent, abandoning any hopes of a British project during the war. With Churchill's backing, he attempted to ensure that every request from Groves for assistance was honoured. While the pace of research eased as the war entered its final phase, scientists were still in great demand, and it fell to Anderson, Cherwell and Sir Edward Appleton, the Permanent Secretary of the Department of Scientific and Industrial Research, which was responsible for Tube Alloys, to prise them away from the wartime projects in which they were invariably engaged. A British Mission led by Akers assisted in the development of gaseous diffusion technology in New York. Another, led by Oliphant, who acted as deputy director at the Berkeley Radiation Laboratory, assisted with the electromagnetic separation process. As head of the British Mission to the Los Alamos Laboratory, Chadwick, and later Peierls, led a multinational team of distinguished scientists that included Sir Geoffrey Taylor, James Tuck, Niels Bohr, William Penney, Frisch, and Fuchs. Four members of the British Mission became group leaders at Los Alamos. Penney observed the bombing of Nagasaki on 9 August 1945 and participated in the Operation Crossroads nuclear tests in 1946. A major strain on the Agreement came up in 1944, when it was revealed to the United States that the United Kingdom had made a secret agreement with Hans von Halban to share nuclear information with France after the war in exchange for free use of patents related to nuclear reactors filed by