Austin K3 Utility Van. Photo credit: Richard Hearing
Good.
"This particular vehicle was registered in London and received into regional store in October 1947. It is believed that this is where it gained its current markings of XII Regional Column, Civil Defence Reserve. It was restored by the Imperial War Museum in 1983."
(From the Museum plaque).
https://www.iwm.org.uk/collections/item/object/70000263