With Watson-Watt and Wilkins pioneered radar in England in 1935. Played essential part in subsequent all-important development. (Contribution recognized by British Government by award of O.B.E. and special grant of £12,000). Appointed Chief of Radiophysics Laboratory in 1946 and transformed it from a radar development establishment to one in which no less than three phases of its work (radio astronomy, rain physics and radio aids to navigation) have acquired international reputations. Personally mainly responsible for:- (i) The development of several radar aids to aerial navigation. (This was recognized by Thurlow Award given by American Institute of Navigation for ""the most outstanding contribution to the science of navigation during 1950""). (ii) Important advances in rain physics, particularly in the recognition of the importance of coalescence between drops as a rain-forming process, in personally undertaking and stimulating aircraft observations of clouds and in studies of the role of freezing nuclei in rain formation.