British Transport Police (BTP) are investigating after a pensioner apparently put a child in an armlock on a train - after he refused to take his feet off the seats.
The incident occurred on a Northern Rail service from Clitheroe to Manchester Victoria on Friday.
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According to the Daily Mail, the boy had been travelling with two other youngsters, aged between eight and 11, who had joined the service at Blackburn.
A 17-year-old student who witnessed the scene said the boys were being "cocky".
According to the Manchester Evening News, the student said: "He threatened them with a 'clip around the ear' and then went and sat back down.
"The children then put their feet back up and wouldn't take them down. The guy then went over again and tried to take their feet down."
Another onlooker on the train took to Twitter to say the children had been misbehaving.
According to the Metro, she wrote: "Kids were badly behaved and no parents but only about eight to 10 years - three boys. Man acted like US cop. Kid crying."
Northern Rail said it is investigating the incident along with the BTP.