Distinguished for his many contributions to the study of the cosmic radiation through a wide-ranging series of experimental investigations and critical analyses of cosmic ray data. Well known for his development of two novel techniques: the neon flash tube, a visual detector of great stability used widely in spectrographs and cosmic ray neutrino and quark studies, and the 'solid iron' spectrograph. Internationally recognised as the leading authority on muon spectra and charge ratios at ground level and at various depths underground in the energy range 5 x 10 [to the power of] 8-10 [to the power of 13] eV, measurements which are among the most basic data of cosmic rays. Measured the spectra of cosmic ray protons, neutrons and pions and from these data and the muon spectrum determined the primary spectrum and K/pi ratio. Results on the interactions of muons were of importance in a number of other investigations, e.g. in the Davis experiment on solar neutrinos. Introduction of the neon flash tube technique to the Indian and South African experiments on cosmic ray neutrinos was decisive and led to the clear identification of neutrino interactions and the determination of the cross section as a function of energy. Has established recently fine astrophysical groups in Durham which have already made useful contributions to the theory of the propagation of cosmic rays in the galaxy, to the explanation of the ultra-high energy end of the primary spectrum and to the origin of the gamma-ray background radiation. His optical group under Scarrott has recently obtained a beautiful map of the galaxy M82 in Rayleigh scattered light, and from it an accurate position for the luminous nucleus.