Dr Cowley has a considerable international reputation for his pioneer work on high-resolution electron diffraction and structure analysis. He is distinguished for:- the initiation and development of single-crystal structure analysis by electron diffraction, including new experimental methods and theoretical techniques; the development (in collaboration with A.F. Moodie) of a Completely new formulation of physical optics, which has, in particular, advanced considerably the theory of electron scattering; the discovery), interpretation and realization of the significance of the new optical phenomenon of Fourier images (in collaboration with A. F. Moodie); the first measurements of short-range order in single crystals of alloys and significant advances in the theory of short-range order.