Thanks, Brendan. I don't usually make much of an effort with Genius puzzles (typically give up after an hour or so), but due to the midweek holiday spent significant time on this one.
The more I think about this the better I think it is. I also did not immediately get the allusion at the end of the preamble (and it is not needed to complete the puzzle), but what a tour de force!
thanks jono and brendan - I had looked at the inside circle but obviously didn't start in the right place ... was puzzled by the clue to 25 which seems to have either "end" or "dying" doing double duty. Suppose there's no rule against that ...