Hi Maurice,
Well, it was luck more than anything, as i am familiar with the scout car, and the trailer, I had worked on when they were still in service, hole for starting handle was giveaway!
Nice to come up with evidence of No.2 Brown on the Humber, I have also come up with the same on the Mk4 A/car.
You will have to make the next riddle, non-British, and I might struggle on it