Well, I can tell you it's the Adro Special, supposedly built in 1938 (I'll need to check) and it's powered by a 998cc JAP with an inlet-over-exhaust homebuilt conversion.
What else do you need?
PS It was indeed 1938, the engine size should be 980cc, and it was based on a GN chassis. As you have said, it's featured quite extensively on the internet, but sadly only on photo image sites, so details are sparse.
PPS The present owner/driver is Colin Rodgers. I have checked the archives of two very well-known internet sites which would be interested in this type of car, and there were zero returns. It has become fashionable in these days for enthusiastic vintage car racers to construct new vehicles from old parts in the spirit of racing in the 1930s. Nothing wrong with that, they're all great fun, especially the aero-engined cars - I'm beginning to wonder if Mr. Rodgers himself built this car from a 1938 Frazer Nash or 1938 JAP motor.