His research has focused on the study of defects in metals, particularly in relation to mechanical properties and phenomena associated with radiation damage. His early research involved theoretical analysis of dislocations in isotropic and anisotropic media, culminating in the monograph 'Anisotropic Continuum Theory of Lattice Defects', published with Barnett and Scattergood as an issue of Progress in Materials Science in 1978. For over 30 years he has made extensive use of atomic-scale computer simulation to investigate the defects that form in irradiated metals, the properties of these defects, and the mechanisms by which their interactions with dislocations influence material properties. He has been awarded 57 research grants, has published 280 research papers and is co-author with Hull of the text book ‘Introduction to Dislocations’.