John was widely recognised for his pioneering work applying neutron scattering methods to a variety of complex systems including molecular crystals, liquids, polymers, adsorbed molecules and biological systems. His innovative use of contrast from dynamics, isotopic replacement and spin helped to selectively simplify the scattering patterns of these systems, allowing for a quantitative understanding of their properties.
As well as being a long-time member of the Research School of Chemistry at The Australian National University, John was the first British Director of the Institut Laue–Langevin in Grenoble.
Throughout his career, John was known for his tireless energy and enthusiasm. He was a mentor and a role model to many, always willing to share his knowledge and expertise. He will be sorely missed, but his legacy will live on through the many scientists he inspired and influenced.