I remember well one particular train I was on one dark Saturday evening in the 90s (can’t remember date). It was on the Portsmouth direct line on the down between Milford and Haslemere at line speed. I think the train in question was 442403.
Anyway, suddenly there was a bang and a jolt. I knew something was afoot because the guard went running through the train towards the front. We got to Haslemere and there was an announcement that we would be delayed because of the bang while they checked the train to ensure it hadn’t hit something. After a good while, another announcement said nothing had been found but we would have a further delay while a train heading on the up would run at extreme caution to check out the track we had just run over. After a lengthy delay another announcement said that nothing had been found so my train would continue to Portsmouth.
Now the driver of following train on the down, I believe, found multiple tripping while trying to maintain power. That train got to the Milford area and stopped, uncommanded. The driver got out and found that the third rail behind and in front for several hundred yards had been displaced/turned over.
It always made me wonder how close, that night, my train came to an accident if the third rail had fallen onto the running rail rather than into the space between the two tracks.
I’m guessing there’s an old report into it somewhere in the industry.