Very sad news indeed.
Like so many of us I enjoyed his talks on the history of astronomy, had some really nice chats with him, including when he mentioned his research into the history of medicine and surgery.
I will treasure the books that he signed for me.
One of my most enjoyable memories is of his talk on ‘Captain Cook, maritime history and navigation’ presented in the hold of the H.M. Bark Endeavour Replica at Stockton-on Tees. We arrived early and one of the local organisers asked me: “Excuse me, are you Allan Chapman?” 🙂
Allan is irreplaceable.
Alex.