The 19-year-old was travelling on the 10.10am service from Glasgow to Paignton when he became involved in an argument with another passenger. He was stabbed in the chest and died before he could receive medical attention.

Train staff locked the alleged suspect, a 21-year-old man from Skelmersdale, Lancashire, in the carriage.Witnesses said the man then broke a window and got out of the train as it approached Oxenholme station in Kendal, Cumbria. He was arrested five miles away.

A British Transport Police source said the victim, from Gloucestershire, had been attacked after becoming involved in an argument between a man and a woman. There were unconfirmed reports that the couple were with three small children and had been arguing loudly.

Officers were last night tracing the victim’s relatives, and police said they would not release further details until his family had been informed.

British Transport Police are introducing airport-style metal detectors at rail stations in a bid to reduce knife crime.

Officers are also using hand-held scanners as part of Operation Shield, which was piloted successfully in London, Liverpool and Birmingham.

A spokesman for Virgin Trains confirmed more than 200 people were on board when the attack took place. “The train manager saw someone had been stabbed and moved people out of the carriage. He then locked the interconnecting doors, leaving the suspect inside,” he said.

British Transport police said the victim died between Penrith and Oxenholme. Residents in the village, known as the “gateway to the Lakes”, were shocked to hear about the killing.

Harry Challinor, landlord of the Station Inn in Oxenholme, was warned by police that they were looking for a suspect.

“An armed WPC called round to search the hotel. She said a man who was about 21 had escaped from the train and was on the run,” he said.

“They wanted to check the sheds and outbuildings and warned us if we saw him he was dangerous and we should not approach him.

“We didn’t know what had happened. Oxenholme is a tiny place and this kind of thing does not happen here.”

Passengers, who were taken off the train at Oxenholme, spoke of panic and confusion and some were treated for shock. Initially, witnesses reported that the victim had been travelling with his girlfriend, but police later clarified this was not the case.

A man arrested in connection with the stabbing was last night being questioned by police.

The incident occurred nine days after Kiyan Price, 15, was knifed to death outside the gates of his north London school.

On Friday another 14- year-old schoolboy was stabbed yards from his school in Birmingham. The youth is in a serious but stable condition.

In a separate incident a 26-year-old woman was seriously ill in hospital last night after she was stabbed outside a nightclub.

The woman, from Ilford, east London, received a single stab wound to her body after being caught up in a brawl outside the Circus tavern in Purfleet, Essex.

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