EVERY train commuter knows that sinking feeling on the late journey home when they find themselves sharing a carriage with an antisocial passenger.

But an incident aboard a ScotRail Edinburgh-Perth train has become an internet sensation after a burly passenger was filmed intervening to throw off a student who was holding up the train after refusing to pay his fare.

The two-and-a-half-minute video, filmed last Friday night and already viewed 200,000 times, shows the ticketless teenager swearing at an elderly conductor who is warning him to pay up or get off the train.

The young man, who named himself on Facebook last night as 19-year-old Heriot Watt student Sam Mains, had only a single Polmont-Edinburgh Park ticket, not valid for his return journey.

In the clip, entitled "ScotRail No Ticket", the white-haired ScotRail worker tells the youth: "I'll sit here all night pal. I'm getting paid for this but they [passengers] will start moaning."

The video continues with the youth protesting his innocence and claiming that he has shown the ScotRail employee his "f*****g ticket".

As the exasperated conductor berates the beanie-wearing student, asking "Why should they pay and not you?", another passenger who had been sitting further down the aisle is seen getting up and coming to the conductor's aid.

He asks the conductor "Do you want me to get him off for you?" before grabbing the teenager by the scruff of his neck and frogmarching him off the train, holding him back at the door as the student tries repeatedly to barge his way back on to the train.

His action was welcomed by rounds of applause from his fellow passengers as the man, who got off the train in Stirling, returned to his seat.

The man who filmed the video, IT teacher Ian Helms, said the mystery hero was a "strong and silent" type who made almost no conversation with other passengers, who were all chatting about the incident.

Mr Helms said: "I'm firmly behind the big man, but everyone is entitled to their own opinion."

Last night student Mr Mains claimed on his Facebook profile to be the youth in the video. Posting on the site, he said: "There's a video ae me on YouTube hahahahaha! ScotRail no ticket".

A friend of the teenager, who asked not to be named, said: "It was handled all wrong. A grown man throwing a wee laddie off a train is a disgrace."

A ScotRail spokesman said: "While we welcome the public's support of our zero-tolerance stance on anti-social behaviour, our staff are trained in conflict management and we do not expect members of the public to take matters into their own hands.

"We are investigating the incident, which appears to show a person travelling without a valid ticket, refusing to pay for the journey, and swearing at a staff member in full view of customers."

A spokesman for British Transport Police said they had not received a complaint from either party since the incident.

The spokesman added: "We are aware of the YouTube video and our inquiries are ongoing.

"British Transport Police did not receive a complaint from anyone on the train at the time the incident is believed to have taken place."