Many , many instances one could quote.
One of my drivers on the down DC line stopped beyond Kensal Green tunnel one evening and picked up a confused old lady (she was between the WCML lines and the DC lines) , who was convinced she was in a wood outside Vienna picking wild flowers with her mother before WW2. She had absconded from secure accommodation but it was a mystery how she got there. With remarkable and commendable persuasion he got her up into the 313 and safely dealt with. When I thanked (and commended him) , he said it was only right as she was someone's grandmother or mother.
A more unfortunate one was the jewelled and studded punk , pissed or something else , who waiting for the last eastbound at Camden Road decided "western style" to listen to the rails thrumming for the train. Regrettably he chose the wrong rail and you can imagine the result.
I would have thought in the 4ft - if the AWS magnet does not get you , before that an obstacle deflector / mini snow plough blade would be in the way.