The cavity magnetron was developed in the Department of Physics by Sir John Randall, Harry Boot and James Sayers. This was vital to the Allied victory in World War II. In 1940, the Frisch–Peierls memorandum, a document which demonstrated that the atomic bomb was more than simply theoretically possible, was written in the Physics Department by Sir Rudolf Peierls and Otto Frisch. The university also hosted early work on gaseous diffusion in the Chemistry department when it was located in the Hills building.