I would say that the vehicle started life as an early 2a,wipers through screen frame,type of frame mount, door hinges,axle drive flange on rear all point to that.
All front bodywork [except wings] along with the top sides, roof,front and rear bumpers, are likely a non rover special conversion for a specific job. Rear lamps moved to make room for jerry can holders.
Vehicle may have worked in remote woodland given the various fittings and what looks like a PTO belt drive [ to work a saw] on the rear.
Some bits point to it having started life in the military.
The 1970's P plate is misleading but this may be the year it was registered after end of military service.