Right then, the first photo shows a glimpse of the rear of a Humber, to be precise, FV1622 Truck, 1 ton, Missile test, 4x4, Humber, then under the tent I believe, is its companion trailer, ie. FV2308® Trailer, 1/2 ton, Functional Test Unit.
The truck had a HP air compressor and alternator driven from the PTO, this suppled power to the trailer, for its role in missile testing.
The photo with item marked "B" is I think, the rear doors to FV1621, Truck, 1 ton, Missile Supply, 4x4, Humber
Yes well done Richard I knew I could rely on you for a comprehensive response, absolutely correct. We could do with chaps like you in MI 10 attention to detail & all that sort of thing ;-)