the Octagon Conference. In the wake of a string of Allied victories, thoughts turned to post-war planning. Afterwards, Roosevelt and Churchill spent some time together at Roosevelt's Springwood estate in Hyde Park, New York. They discussed post-war collaboration on nuclear weapons, and on 19 September signed the Hyde Park Aide-Mémoire, detailing the agreement resulting from what they discussed. Most of this dealt with Bohr's thoughts on international control, but it also provided that "[f]ull collaboration between the United States and the British Government in developing Tube Alloys for military and commercial purposes should continue after the defeat of Japan unless and until terminated by joint agreement." Of Roosevelt's advisors, only Hopkins and Admiral William D. Leahy knew of this secret wartime agreement, and Leahy, possibly because he never believed that the atomic bomb would work, and was therefore perhaps not paying much attention, had only a muddled recollection of what had been said. When Wilson raised the Hyde Park Aide-Mémoire in a Combined Policy Committee meeting in June 1945, the American copy could not be found. The British sent Stimson a photocopy on 18 July. Even then, Groves questioned the document's authenticity until the American copy was located many years later in the papers of Vice Admiral Wilson Brown, Jr., Roosevelt's naval aide, apparently misfiled in Roosevelt's Hyde Park papers by someone unaware of what Tube Alloys was, and who thought it had something to do with naval guns or boiler tubes. End of the Quebec Agreement Truman, who had succeeded Roosevelt on the latter's death on 12 April 1945, Clement Attlee, who had replaced Churchill as prime minister in July 1945, Anderson and United States Secretary of State James F. Byrnes conferred while on a boat cruise on the Potomac River, and agreed to revise the Quebec Agreement, with a view to replacing it with a looser form of co-operation on nuclear matters between the three governments. Groves, Secretary of War Robert P. Patterson and Patterson's advisor George L. Harrison met with a British delegation consisting of Anderson, Wilson, Malcolm MacDonald, the High Commissioner to Canada, Roger Makins from the British Embassy in Washington, and Denis Rickett, Anderson's assistant, on 15 November 1945 to draw up a communiqué. They agreed to retain the Combined Policy Committee. The Quebec Agreement's requirement for "mutual consent" before using nuclear weapons was replaced with one for "prior consultation", and there was to be