David Gubbins has conducted important work on theoretical geophysics, especially on the history of the Earth’s magnetic field. He has used historical records and modern geophysical inverse theory to study the evolution of the magnetic field. The maps he has obtained for the field at the core–mantle boundary more than 100 years ago are as detailed as present day maps from satellite data, and have opened up a new field concerned with the fluid dynamics of the core. He has also made important contributions to dynamo theory and to seismology.