 Significant contributions to the war effort included the development in 1940 of the cavity magnetron for radar, by the scientists John Randall and Harry Boot at the University of Birmingham, as well as advances in communications technology and the ongoing mass production of valves, lamps and lighting equipment.The post-war years saw a decline in GEC's expansion.After the death of Hugo Hirst in 1943, his son-in-law Leslie Gamage (elder son of the founder of Gamages), along with Harry Railing, took over as joint managing directors.