This was actually built for the planned German invasion, a British misinformation campaign had convinced them that fairground wall of death shows where actually disguised AA gun sites.
The idea was to drive in through the little door, then wizz round causing havoc within!
They where clearly built on one half of a very early BobCat loader frame, but due to an oversight by the designer, the skid steer did not work!
Except for this prototype which kept falling over, they all disappeared into infinity during testing!!