I once came upon one of those tall sailing boat trailers on the M25, clockwise at the M20 junction. I was in the minibus with nine of us on board.
It was undergoing a cyclic vibration, the whole shebang rocking from side to side getting steadily worse until light appeared under each wheel. It then slowed, abated and towed straight for a hundred yards before wobbling and starting all over again.
I slowed down and followed him (didn't want to miss the opportunity of being witnesses!) until he turned off down the M3. I'm morally certain that he was utterly unaware there was anything wrong!
regards,
Kim Siddorn.