With the shortage of vehicles in 1940, Concrete Ltd developed and built the Bison Concrete Armored Vehicle.
None of the vehicles were the same as any truck that could be scavenged was convereted.
Many of the chassis were AEC, Dennis, Leyland, or Thorneycroft pre-war trucks. These had wood placed for the bodies and then up to 6" / 152 mm of concrete poured over the top. This made the vehicle bullet proof and could handle hits from guns up to 37 mm.
Two types were constructed. One with concrete over the engine and cab and then a pillbox mounted on the flatbed of the truck chassis. The second type had concrete completely covering the cab and flatbed covered in concrete with the only entrance being a trapdoor underneath.
Typically these concrete armored vehicles could carry between 5 and 10 men and the heaviest armament being a light machinegun.