This is the CC Sudbury Hill Climb, which is also the East District Championship. It's been held every since (I think - there may possibly have been a gap or two at some point!) the mid 80s on Watson's Hill, Semer, not far from Hadleigh in Suffolk. It's a short hill - only 400 metres - but reasonably steep, at a maximum of 11%. It therefore tends to favour riders who can generate heaps of power for short distances.
This year's event took place on closed roads on September 29th, with the event having gradually moved further forward in autumn to the point where it's almost now a summer event. The weather, though, had other ideas: I think it's been held on warmer days in November!
It was won by Oskar Everett, with Kirstin Hamilton taking the women's prize. The full results are at https://www.cyclingtimetrials.org.uk/...