As I have said before, its the actual weight of the trailer behind the car that matters NOT the plated maximum.
I was stopped on the M6 by the most (Trailer wise) switched on copper I have ever met. I was towing my empty 3500kg trailer with my wifes CRV (Only rated to tow 2000kg). Trailer on its own weighs 700kg. He checked the plate on the trailer, checked the max tow weight of the car (plate on door jam), checked some kind of database via his radio. No issues at all. He was actually looking for a stolen trailer.
But he did ask if I towed the boat with the CRV
I am 99% certain that all this hot air flying round the internet regarding tow cars with tow weights to match or exceed max plated weight on trailers is rubbish. But I am happy to be proved wrong, can anyone actually show me the piece of legislation ?