In October 1959 Gregorio obtained a grant from the United States Atomic Energy Commission to construct a machine to record automatically the polarisation of fluorescence of a molecule as a function of the wavelength of the exciting light and I was given the task of producing the spectrometer.

Unfortunately, by the time the machine was created in 1961, for reasons that have been given elsewhere, Gregorio had decided to emigrate to America so whatever the substantial program of its use Gregorio had decided on was never put into effect. By this time too my own interests veered briefly towards haemoglobin kinetics where Quentin Gibson had been my mentor and then, for the rest of my career to enzyme kinetics. As a result I never had the opportunity to collaborate in a meaningful way with Gregorio’s research on proteins and biological systems in general.

Nevertheless, I had ample opportunity to appreciate the remarkable quality of Gregorio’s mind and, more particularly as it concerned me, his personal character of geniality, wry humour and above all generosity. Even after 50 years he still holds a real presence in my mind and I am grateful indeed to have known him.