I've seen a tank fall of a low loader whilst going round a roundabout on the A303, tank fell off and buried the barrel into the road. I was about 3 cars behind. Just before they closed the road i passed it (2 wheels on grass).
My parents 5 minutes behind got stuck for 3 hours before they could winch the challenger tank into a safe place. They opened the road for 1 hour then closed it from 22:00 to 07:00 to recover it.