This is a photo of a Crossley '1940 pattern' foamer at RAF Museum Cosford:
Note the step on the front mudguard: I may be 10,000% wrong again but that photo at the top looks as though it may have been a prototype of 1938, especially as it has a wooden 'body' of the type used on WD trials vehicles of the period. It also has Trade Plates attached which the other 1938 WD trials chassis used if they did not have Middlesex CC regos/WD Census Numbers.