Historical:

Made by the Rootes Group, the Humber was essentially a combination of the Karrier KT 4 artillery tractorchassis and the armoured body of the Guy Armoured Car. The KT4 was already in production for the Indian Army, and Guy were having problems with the production levels required. The Karrier name was dropped to avoid confusion.

The first order for 500 was placed in 1940. The first Humbers were more or less identical to the Guy down to the faults in armour but this was rectified. Production started in 1941.

The Mark III improved upon the Mark II by providing a three-man turret. Mark III production ended in 1942 after 1,650 had been built. With a possible replacement, the 2-pounder armed Coventry armoured car, on its way, the Mark IV was designed. This put the US 37 mm gun in the turret but at the cost of one crewman. The Coventry was not ordered as a replacement and so production of Mark IV continued, for a total of 2,000, despite its flaws.

Info: Humber Armored Car Mk. IV 8th Infantry Division, Sangro River, Italy, 1943