I knew David when he was a teenager at Winchester College and had the pleasurable task of helping him acclimatise to a quirky English public school from the liberal Dutch School that he had been attending. David was unphased by the transition and very rapidly showed his mathematical genius. I remember we both enjoyed electronics; he designed a logic system on a sheet of paper to play Tic Tac Toe, and we then jointly constructed it using TTL 7400 ICs, and it worked! This must have been David's first venture into practical electronics, and look how far he went from there. I lost touch with him after we left school, but read of his sad early death in our school magazine. What a great loss; he was a uniquely intelligent man and, by all accounts, a legend in his own lifetime.