John Rowell has made significant contributions to low-temperature physics and superconducting tunnelling and its applications, in particular. John made the first observation of the Josephson effect, in association with Philip W. Anderson, and noted its extreme sensitivity to magnetic fields, later utilised in interference devices (SQUIDS). He was granted the first patent describing the use of Josephson junctions as logic and memory devices. With theoretical collaborators, John converted the tunnelling characteristics of normal metal–superconductor tunnel junctions into a quantitative spectroscopic technique for the investigation of electron–phonon coupling. This technique has been widely exploited and has now been applied to numerous systems. This resulted in John and the late William L. McMillan being awarded the 1978 Fritz London Memorial Prize for Low Temperature Physics. John and his group have contributed to the technology of Josephson junctions and have investigated phonon spectra in metallic superlattices. His group also pioneered studies of localisation and the metal–insulator transition in thin metal films and co-deposited metallic mixtures — systems which are now extensively used in this field.