remained committed to this policy in the immediate post-war period. The RAF adopted the Avro Lincoln, an updated version of the wartime Avro Lancaster, as its standard bomber for this purpose. Production of the Lincoln continued after the war, and eventually 450 were built. Although touted as a mighty bomber in 1945, it lacked the range to reach targets in the Soviet Union, and would be vulnerable to the new jet fighters that were then under development. Elements within the RAF and the government sought to adopt the new nuclear weaponry and advances in aviation technology to introduce more potent and effective means of conducting warfare. In November 1944, the UK Chiefs of Staff had requested a report from Sir Henry Tizard on potential future means of warfare. Reporting without knowledge of the progress of Allied efforts to produce an atomic bomb, in July 1945 the Tizard Committee urged the encouragement of large-scale atomic energy research. It foresaw the devastating effects of atomic weapons and envisaged high-flying jet bombers cruising at at . It was thought that potential aggressors might be deterred by the knowledge that Britain would retaliate with atomic weapons if attacked. Even at the time, there were those who could see that guided missiles would eventually make such aircraft vulnerable, but development of such missiles was proving difficult, and fast and high-flying jet bombers were likely to serve for years before there was a need for something better. Massed bombers were unnecessary if a single bomber could destroy an entire city or military installation with a nuclear weapon. It would have to be a large bomber, since the first generation of nuclear weapons were big and heavy. Such a large and advanced bomber would be expensive on a per-unit basis, as it would be produced in small quantities. During the early part of the Second World War, Britain had a nuclear weapons project, codenamed Tube Alloys, which the 1943 Quebec Agreement merged with the American Manhattan Project. The British government trusted that the United States would continue to share nuclear technology, which it regarded as a joint discovery, after the war, but the United States Atomic Energy Act of 1946 (McMahon Act) ended technical co-operation. The British government saw this as a resurgence of United States isolationism, as had occurred after the First World War, and dreaded the possibility that Britain might have to fight an aggressor