Bedford QLB Bofors Gun Tractor designed to tow a 40mm AA gun along with crew of 7 and kit.
The lower long boxes behind the crew cab are for ammunition, whereas the smaller ones on top are for crew kit, with the two back ones for vehicle/gun equipment.
It has a straight six 28hp engine and as such is fairly under powered - this one does about 7 miles to the gallon (petrol). With a gun in tow, that would drop to about 5mpg.
Of the 5000 odd manufactured, I know of about ten that survive world wide, there are, to my knowledge three complete ones in the UK two of which (counting this one) are in Essex, both owned by Essex HMVA members. I found it in a scrap yard near Braintree. It has been restored in the markings of the Guards Armoured Division during the D Day period.