The Factory Ledgers say it was delivered to the Automobile Association painted yellow on 7/6/39 with engine KM20 1657 fitted.
There is a story that a large group of AA men were transferred to the Corps of Military Police early in the war as traffic controllers and they may have taken their BSA combinations with them?
Rob there is a guy on HMVF who is thinking of selling this (KM20) I suggested it looks more like a WM20 and asked for numbers. So far he's only provided frame number. Ron