the presence of a team of refugee French scientists led by Hans von Halban, Oxford also had the world's main supply of heavy water, which helped them theorise how uranium could be used for power. In July 1941, the MAUD Committee produced two comprehensive reports that concluded that an atomic bomb was not only technically feasible, but could be produced before the war ended, perhaps in as little as two years. The MAUD Committee unanimously recommended pursuing its development as a matter of urgency, although it recognised that the resources required might be beyond those available to Britain. But even before its report was completed, the Prime Minister, Winston Churchill, had been briefed on its findings by his scientific advisor, Frederick Lindemann, and had decided on a course of action. A new directorate known by the deliberately misleading name of Tube Alloys was created to co-ordinate this effort. Sir John Anderson, the Lord President of the Council, became the minister responsible, and Wallace Akers from Imperial Chemical Industries (ICI) was appointed its director. Early American efforts The prospect of Germany developing an atomic bomb was also of great concern to scientists in the United States, particularly those who were refugees from Nazi Germany and other fascist countries. In July 1939, Leo Szilard and Albert Einstein had written a letter warning the President of the United States, Franklin D. Roosevelt, of the danger. In response, Roosevelt created an Advisory Committee on Uranium in October 1939, chaired by Lyman Briggs of the National Bureau of Standards. Research concentrated on slow fission for power production, but with a growing interest in isotope separation. On 12 June 1940, Vannevar Bush, the president of the Carnegie Institution of Washington, and Harry Hopkins, a key advisor to the president, went to the president with a proposal to create a National Defense Research Committee (NDRC) to co-ordinate defence-related research. The NDRC was formally created on 27 June 1940, with Bush as its chairman. It absorbed the Advisory Committee on Uranium which had gone beyond its original role and was now directing research. It became the Uranium Committee of the NDRC. One of Bush's first actions as the chairman of the NDRC was to arrange a clandestine meeting with Air Commodore George Pirie, the British air attaché in Washington, and Brigadier Charles Lindemann, the British Army attaché (and Frederick Lindemann's brother), to discuss a British offer of a