DEANB:
Chew Bros mercedes.Only single wheels on the trailer,most were double back then.6
It’s a lightweight trailer design, either a Pitt Tandem-4, or a similar type made by Primrose. The restricted the GTW to 26 tons. With a light unit coupled to one of these the payload was only a couple of tons less than a 32 tonner. E.G. an AEC Mercury tractor unit plus Pitt tandem-4 we ran tared off at 7 tons, so a legal 19 tons payload. Mr Bewick had a similar take on getting a quart out of a pint pot in his early years.