Formerly a Fellow of St. John's College, Cambridge and lately Reader in Theoretical Physics in the University of Liverpool. His early work made contributions to abstract field theory. In recent years he has developed the theory of emission of particles from excited nuclei so that it has become possible to use the relevant experiments for a quantitative determination of the density of energy levels of nuclei. While occupied with this work he was able to develop quantitatively a method for the extraction of the beam from a synchrocyclotron which was very successful in the Liverpool machine and is being adopted for most others.