Vince, the "trailer" was a very well executed mock up complete with pretend hitch and red painted "lights". Never, ever going on the track!

The same trailer and welfare cabin combination is currently on show at the Plantworx exhibition at Bruntingthorpe. (I visited yesterday). I concur with James that the trailer is a very good mock-up and had me going until I saw the sign on it saying that it was for demonstration purposes only.