I was at the epicentre of an accident on the northern approach once. Circa 1983. I was in the front passenger seat in a 3 litre Capri bombing down the third lane at about 80mph (and not feeling entirely comfortable as we entered the 30mph zone) when a yellow van pulled out of the middle lane without indicating and smacked us into the central reservation. The front-right of the car scrunched up to just in front of the driver's feet and span round into the middle of the road where miraculously no-one hit us. We both jumped out unscathed.
Not sure how far the tailback went that day, but my mate had to phone his dad to explain what had happened to his dad's brand new car. "Can you drive it home?" his dad asked.