Hi J
The question would be who he actually worked for - to my understanding many of the company's vehicles were impressed into service, so it may simply be a case of a commercial vehicle. If it was camo military vehicles the RAF had a number of "tenders" they used and the army used a selection of Bedford, Morris, Leyland etc. vehicles. There were special vehicles for torpedoes and sea mines, often on Fordson chassis. Austin was popular with the RAF and they had a "bomb-flat that was used on the bases, but not sure if they fetched the ammo from the factory. Trains were also used with diesel engines.
That's just my 2c worth