Distinguished for his work on palaeomagnetism. By training a physicist, he has collaborated closely with geologists and geochronologists and has attacked the subject from the point of view of global geology of which he has now a profound knowledge. His early important contributions related to establishing the pattern of polar movement with respect to Africa. Since coming to Australia, he has determined these patterns also for Australia, India and Madagascar, enabling the past reconstruction of the southern supercontinent of Gondwanaland to be established beyond doubt. His background in physics has enabled him to make improvements in instrumentation and in the theories of magnetic domains and their effects in rock magnetism. He has been one of the pioneers in combining palaeo­magnetic information with the theory of plate tectonics. His book 'Palaeomagnetism and Plate Tectonics' has been widely acclaimed and is now the standard work on the subject. More recently he has been applying the results of palaeomagnetic studies to aspects of the origin of the geomagnetic field and dynamo processes in the earth's core. This is the first attempt to bridge the wide gap that currently exists between experimenters and theoreticians in this field.