During the early part of the Second World War, Britain had a nuclear weapons project, code-named Tube Alloys, which the 1943 Quebec Agreement merged with the American Manhattan Project to create a combined American, British, and Canadian project. The British Government expected that the United States would continue to share nuclear technology, which it regarded as a joint discovery, after the war, but the US Atomic Energy Act of 1946 (McMahon Act) ended technical co-operation. Fearing a resurgence of United States isolationism, and Britain losing its great power status, the British Government restarted its own development effort, under the cover name "High Explosive Research".