Hi Wally, I think that must have been a prototype or trials vehicle, the production run had fixed front arches, large rear mudguards and a large equipment locker behind the cab. Most if not all the production trailers had three non folding ramps in place of the two ramp one shown.
See here for another view of the 30 ton Scammell that came to grief on a weak bridge: http://www.creopcrown.co.uk/Units/Others/RCT/rct.html