Not at all sure why you all think I recently changed the clutch!
BUT - it usually loses a bit of oil, and it hasn't - could the filter be blocked and not enough oil circulating? Just an odd thought that poppeed into my head.........
i think most of us mistook the "id put a new clutch in" in your 1st post

most things still apply though, eg loose nut, worn basket ,
cable? didnt the AA man check it?it should be the 1st thing to check,fraying, lubed etc, has it been crushed in the headstock area?, trikes use the steering more than bikes, its common things wearing around here
i take it you have ridden with the trailer before? if not, try it without?
oil not circulating as it should? no, your engine would be dead now,
stop thinking too much, , and check one thing at a time, until you find a problem, will be far easier