Well, I was sure it was a Autocar based truck, and I am sure DAF is the marque of this vehicle. DAF produced trailers and modified trucks for special pourposes before WWII. So, if this truck would be bodied by Van Twist, we should believe that the base is a '51 Daf...but I don't think so.
So I suppose that Pguillem's answer is the correct one, and I give him the point. Sorry Gerd...if you should find any proof about Van Twist connection, I'll be glad to award you another point.