During the Second World War, Britain commenced a nuclear weapons project, known as Tube Alloys, but the 1943 Quebec Agreement merged it with the American Manhattan Project. Several key British scientists worked on the Manhattan Project, but after the war the American government ended cooperation on nuclear weapons. In January 1947, a cabinet sub-committee decided, in response to an apprehension of American isolationism and fears of Britain losing its great power status, to resume British efforts to build nuclear weapons. The project was called High Explosive Research, and was directed by Lord Portal, with William Penney in charge of bomb design.