Many years ago I stopped behind a sturdy Rover of some sort which had stopped for a lollipop lady conducting a crocodile of what seemed like an entire school of children across the road. Suddenly the bloke in the car on the other side of the crossing started flashing his headlights. I had just time to glance in my mirror and WHUMP! a Volvo had made my little Fiat the filling in a sandwich ... Fortunately, as it happened, the crumpling of my Fiat had prevented the Rover from being pushed into the crocodile of kids.
The driver claimed he 'didn't see' the stopped traffic on both sides of the road, the lollipop lady's lollipop, the crocodile of children on the pavement on both sides and across the road, the accompanying adults in high vis about every tenth child...
Neither I nor the driver of the Rover lost our no claims bonus - his car was repairable, mine was a write-off, and I'd not had it long - but I was led to understand that the driver of the Volvo - whose car sustained only minor cosmetic damage - was 'strongly advised' to relinquish his licence and his family were in full agreement that he would.
Both I and the Rover driver were thankful, in an odd sort of way, that we had been there in that position at that time, as our presence by chance had prevented something truly awful from happening, at the cost of only some inconvenience to us.