THE student who was bundled off a train by a fellow passenger after failing to produce a valid ticket was sold the wrong ticket earlier in the day, subsequent investigations have confirmed.

Warning: the YouTube video shown above contains some offensive language

Sam Main, 19, was shown apparently being lifted from his seat and ejected by Alan Pollock after swearing at an elderly conductor. He subsequently claimed he had paid the fare for the journey.

However, The Herald has learned the video was shot following an earlier incident – not shown on YouTube – in which Mr Main allegedly attempted to trip the conductor by putting his leg in the aisle.

It is understood that both Mr Main and Mr Pollock may now face criminal charges in relation to the incident, which occurred on the 9.33pm train from Edinburgh to Perth on December 9.

British Transport Police launched an investigation after receiving a complaint of assault last week by Mr Main, from Falkirk, who is studying building and surveying at Edinburgh's Heriot-Watt University.

The conductor, who has not been named, is on annual leave amid a separate investigation by ScotRail.

Sources close to the investigations have confirmed Mr Main's claim, made last week, that he had tried to buy two single tickets, one from Polmont to Edinburgh Park and another in the return direction (and using his student railcard), because he was unable to use his railcard for the outward journey before 10am.

Mr Main said the conductor at Polmont had instead given him two tickets for the same journey, one full fare and one at a discounted price using his railcard, but it was only when he got on the train that evening he realised he had two Polmont-to-Edinburgh Park tickets.

CCTV footage from the train from Edinburgh shows that an argument broke out after the conductor asked Mr Main for his ticket shortly after departure, sources said.

It shows the conductor stepping over on obstacle after the argument, though the view of the aisle is blocked by another passenger.

It is understood the conductor has claimed that Mr Main tried to trip him by putting his leg into the aisle and said that the student became abusive during the argument and started swearing when asked to produce a valid ticket.

However, the footage uploaded to YouTube was filmed later, when the conductor returned and repeatedly ordered Mr Main to leave the train at Linlithgow, insisting the train would not move until he did.

Though the teenager apparently had a valid defence, he made no mention of having been mis-sold a ticket on the video but swore repeatedly at the conductor and insisted that he had a valid ticket.

A spokesman for ScotRail declined to comment on the situation yesterday, saying: "Our inquiries into the circumstances surrounding the incident continue.

"As British Transport Police has received and is investigating a complaint of assault, it would be inappropriate to comment further."

A British Transport Police spokesman added: "We can confirm we are investigating a complaint of assault. Our inquiries are ongoing."