Origins of British scientific intelligence during World War II (headed by R. V. Jones, with Frank as deputy). Intelligence on nuclear research in Germany; relations with U.S. intelligence (Samuel Goudsmit); comments on Fritz Houtermanns and Carl Weizsäcker. German uranium project and Werner Heisenberg's Farm Hall estimate of nuclear explosive critical mass; postwar German version of their war work; Heisenberg's role in German nuclear research.