Brave soldier Billy McPhail, 26, was standing on a station platform at Strood, Kent, when he saw an elderly woman run for a train and slip.
"I am really not a hero, I just acted on instinct"
The pensioner fell on to the tracks and found herself unable to get up - so Billy leapt down and ran 100 yards to the other side, narrowly missing a passing train as he did so.
Thankfully - and incredibly - the paratrooper reached the woman and managed to lift her back to the platform.
And, despite the fact the 6.05am train was hurtling towards them, he made sure the OAP was safely on the platform before leaping up behind her, as the train slammed to a brake just yards away.
Watch the shocking moment for yourself below.
Billy, who was travelling home to Essex last Thursday after visiting friends in Kent, said to the Mail Online:
"I am really not a hero, I just acted on instinct. I just didn’t think of the dangers.
"I saw her ankle bent the wrong way, so I knew she was hurt and I couldn’t move her on my own.
"I called to another guy to help, he jumped down and other people ran along the platform to try and flag down the train."
Luckily, it managed to stop a few yards away from us at the end of the platform.'
The woman is now believed to be recovering in hospital after an operation on her broken ankle.
Rail operator Southeastern Trains has now launched full investigation into the incident - and a spokesman for the company have warned people of the dangers of jumping onto live tracks.