I was informed of Crockett & Jones UK/US sizing standards by Mr. Huqstable, then Manager of Crockett & Jones mail order department (firstname.lastname@example.org). I guess its possible that you, a C&J customer, is better informed than a C&J manager but I doubt it. Mr. Huqstable's statement to me is objectively proven by the posts of CTBrummie, Gerry Nelson and The7Ups on page 155.
I am not saying that a person who generally wears a UK9 should buy a US9.5; the person needs to try the shoes on and maybe the US9.5 fits or maybe the US10 fits. I am merely stating C&J's basis for marking the US size on their shoes.