The point is awarded to D-type. I'm afraid I know nothing more about the car, although the builder is well-known enough for the various cars he built in the immediate post-war years. There was a Riley-engined single-seater, at least 2 trials specials and I wonder if there were more.
The book's a good one Tobytwirl. The author forgot to provide a proper index but I understand these are now available in retrospect.