Gilbert Lonzarich has made many contributions to the field of metallic magnetism. His early experiments in Canada on the very slight temperature and pressure dependence of the de Haas–van Alphen frequency in iron provided important evidence for the theoretical interpretation of the saturation magnetisation of ferromagnetics at low temperatures. Subsequently, he and his students at Cambridge made important contributions to the understanding of weak ferromagnetics such as Ni3Al and nearly ferromagnetic metals such as Ni3Ga by a combination of de Haas–van Alphen and neutron scattering studies. On the basis of a novel theory of the effect of magnetic fluctuations, he succeeded in obtaining a quantitative interpretation of both the magnetic and thermal properties of such materials. Gilbert combines high skill and originality in experiment (over techniques ranging from metallurgy to electronics and computing) with a profound theoretical grasp.