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I had arrived in Sheffield as a young, inexperienced lecturer. I soon got to know Gregorio because of his interest in his colleagues and in their activities. From the start he wanted to talk about my trivial research problems and ideas and invariably offered profound advice and insight in the narrow field of my investigations. But he also frequently came into my office to talk about his own recent studies and his unique ideas and expanded in detail on them.

 

Inexperienced as I was, I had great difficulties in following his discourse and his arguments and certainly was not in a position to make any intelligent contributions. All the same, when he left he invariably thanked me and left with the comment "Thank you very much, Theo, that was a very helpful discussion". I don't think he ever noticed my embarrassment. He was an extraordinarily generous, kind and modest man; he was of invaluable help later when I tried to apply the fluorescence techniques which he had developed to some of my own studies. His help was also crucial in furthering my post-Sheffield career.

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I owe this outstanding colleague my warmest thanks.