In his early career, he focused on the rotational history and dynamo-generated magnetic activity of cool stars, ultimately producing micro-arcsecond resolution maps of starspot distributions and surface magnetic fields. With Dr R. D. Robinson he co-discovered the centrifugally supported "slingshot prominence" systems in the coronae of the young, rapidly rotating solar-type star AB Doradus and other similar objects.
Planet formation appears to be a natural consequence of the star formation process: 4100 planetary systems comprising over 5600 planets are currently known to orbit stars other than the Sun. Studying the architectures of extra-solar planetary systems is revolutionising our understanding of our own solar system's formation and dynamical history.