An authoritative history of postwar British defence research as related to the establishments that now form part of the Defence Evaluation and Research Agency (DERA). In addition to research towards new weapons, the establishments have maintained high levels of policy relevant expertise, providing advice to the government and even carrying out some manufacturing. This systematic treatment of their history puts the applied science of the military sector in its technological, military and social context. Developments and areas of work have been selected for inclusion primarily on the basis of their importance to Britain's overall defence capabilities and posture during the period. Also included are cases of significance to civil industry and technology in general, together with treatments of key aspects of defence management and organization. A substantial introduction puts the research in its strategic context.