Hi Nigel,
That trailer has a two position tow hitch, it is shown in the lower position. I cannot think now how it was changed over, but the whole drawbar was rotated 180 degs, to bring it to the higher position. It may have been done so that it could be towed by the 1 ton trucks of that period (K9, MRA1, Humber FV1600, etc), as well as Champs and L/Rovers.