Dominic Welsh died late last week.
Dominic and I were tutors at Merton College, Oxford for nearly eleven years. I was the pure maths tutor and he was the applied maths tutor. But there was no other Oxford college where the mathematical interests of the pure and applied maths tutors were closer. College lunches are an opportunity to talk to colleagues in other areas; Dominic and I broke this convention to some extent by discussing our research, though he was in no way an antisocial mathematician!
He had a very great impact on the subject. Much of this came from his provocative conjectures, but the main influence was through his students. Take a look at the Mathematical Genealogy page: his students include Adrian Bondy, Peter Donnelly, Graham Farr, Geoff Grimmett, Colin McDiarmid, Criel Merino, James Oxley, Ken Regan, and David Stirzaker.
Among other things, he was the second chair of the British Combinatorial Committee, my predecessor-but-one in this role.
Peter Cameron's Blog 
Condolences 🌹
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This is sad news. Dominic was my academic grand-father. We shared a birthday and a love of cricket and mathematics. For a more complete academic family tree, see https://users.monash.edu.au/~davidwo/files/Welsh-FamilyTree.pdf.
Sad news indeed. My father went to university with Dominic and they remained lifelong friends. Years ago he introduced me to Dominic and I invited him to come and give a talk at my school on codes and cryptography a few years after the publication of his text book on the subject. He accepted. It was filled with exotic terms like one time pad, entropy, trapdoor systems, and filled with characters such as Alice, Bob, enemies and attackers, like something out of a spy novel. It’s amazing to think how the mathematical technologies that Dominic taught in his text book now touch everyone in the world who uses a phone or the internet. I wonder how many cryptosystem designers and engineers he influenced.
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Take a look at the appreciation of Dominic by Graham Farr, Dillon Mayhew and James Oxley (the link is in the pingback from the Matroid Union).
Ken Regan, one of Dominic’s many students, has written a very interesting tribute: https://rjlipton.wpcomstaging.com/2024/03/01/dominic-welsh-1938-2023/
This particularly concerns Dominic’s work and insights in computational complexity and some of Ken’s own adventures in the field.