The box trailer had been left in a road not far away having had the towing hitch taken off. It was taken by a recovery company who kept it locked up until the SOCOs had checked it for finger prints. I was allowed to go and look at it yesterday. Having taken some dimensions, I set off to buy the parts necessary to recommission it. A hitch, a jockey wheel and a brake bar cost me £260.85 which hurt a bit, and I had to pay £150 to release it from the recovery company.
I spotted the Brompton on eBay, and rang the gent selling it. After he checked a load of details he accepted it was mine and agreed that I could have it back. I collected it this afternoon. I now await the visit by a policeman who is coming to take a statement.