1941, ostensibly to discuss the radar programme, but actually to find out why the United States was ignoring the MAUD Committee's findings. He discovered to his dismay that the reports and other documents sent directly to Briggs had not been shared with all members of the committee; Briggs had locked them in a safe. Oliphant then met with William D. Coolidge, who was acting in Compton's place while the latter was in South America; Samuel K. Allison, a colleague of Compton's at the University of Chicago; Ernest O. Lawrence, the director of the Radiation Laboratory; Fermi and Conant to explain the urgency. In these meetings he spoke of an atomic bomb with forcefulness and certainty. Allison recalled that when Oliphant met with the S-1 Section, he "came to a meeting, and said 'bomb' in no uncertain terms. He told us we must concentrate every effort on the bomb and said we had no right to work on power plants or anything but the bomb. The bomb would cost $25 million, he said, and Britain did not have the money or the manpower, so it was up to us." Bush and Conant received the final MAUD Report from Thomson on 3 October 1941. With this in hand, Bush met with Roosevelt and Vice-President Henry A. Wallace at the White House on 9 October 1941, and obtained a commitment to an expanded and expedited American atomic bomb project. Two days later, Roosevelt sent a letter to Churchill in which he proposed that they exchange views "in order that any extended efforts may be coordinated or even jointly conducted." Collaboration Roosevelt regarded this offer of a joint project as sufficiently important to have the letter personally delivered by Frederick L. Hovde, the head of the NDRC mission in London, but Churchill did not respond until December. He assured Roosevelt of his willingness to collaborate, and informed him that Hovde had discussed the matter with Sir John Anderson and Lord Cherwell, as Frederick Lindemann was now known. The MAUD Committee had considered the issue of collaboration with the United States, and had concluded that while pilot isotope separation plants could be established in the United Kingdom, full-scale production facilities would have to be built in the United States. The British expressed concerns about the security of the American project. Ironically, it was the British project that had already been penetrated by atomic spies. John