Ian Grant has conducted work on relativistic effects in atomic physics, of importance for detailed studies of all atomic systems and particularly for heavy atoms and for highly ionised atoms in laboratory and astronomical plasmas. Ian has made fundamental contributions to the development of the relevant mathematical theory and has shown great skill in writing computer codes which are used worldwide. He has obtained accurate results for energy levels and laid the foundations for important further advances. His current work includes studies of electron scattering from heavy atoms and of the structures of molecules containing heavy atoms. He has also done important earlier work on radiative transfer in stellar and planetary atmospheres.