Peierls' most influential work, written with O.R. Frisch at Birmingham, Mar 1940, stating the case for the feasibility of producing an atomic bomb using the rare 235 isotope of uranium. The importance of the document and its role in the setting-up of the MAUD Committee, the 'Tube Alloys' and 'Manhattan' Projects have been acknowledged in all the histories of the period. Peierls's own brief account is given in Bird of Passage, pp. 152-156.