I had the great privilege of working for David for a few years in Cheltenham. A true gentleman with a strong moral compass and a big heart. I’ll always treasure the memory of collaborating with him on a brief mathematical paper. I also remember him telling me about a paper he had written in which he described a revolutionary way to view mathematical proofs: rather than truth trickling downwards, falsehood would percolate upwards, “like rising damp”, in his memorable analogy My belated condolences on your loss.