I live in outer West London and used to have a 1940 built BSA WDM20, so may know of him?
Sold my WDM20 back in 2001, still miss it, but had great fun with it and used it for a lot of veterans events as well, including 1st Airborne Recce Association reunions when dear old Chalky White was still alive, who had been the 1st AB Recce Don R at Arnhem and was probably the last person to escape from the bridge area back to Oosterbeek, albeit a somewhat hazardous journey by m/c.