NEWMARKET, UK—It's hard not to feel like Christmas has just been cancelled. The Flat turf season doesn't revolve around Newmarket, of course. There are more than 14,000 horses in training in Britain and only about 2,500 of those are based in the East Anglian town, but that does make it the busiest training centre and, as the place where it all began, Newmarket lays claims to being the sport's unofficial HQ. Having emerged from the wettest and windiest of winters with the start of the turf now just days rather...