A train to London was evacuated after a passenger reportedly pulled a knife and threatened a conductor.
The incident occurred shortly after 5pm on Saturday on a Chiltern Railways service from Bicester in Oxfordshire to Marylebone.
The train had just pulled into Haddenham and Thame station when the passenger was pinned to the ground by four police officers and arrested, a witness said.
Passengers were then told to get off the train and join another that was heading towards the capital.
A 23-year-old man was arrested at the scene on suspicion of ABH and is currently in custody, police said.
A witness told the Daily Mail: “Around 50 people had to get off the train and I saw four police officers sprinting across the bridge to get to the man.
“They got onto the carriage, which was next to the one I was on, and managed to pin him down.
“When we were waiting on the platform, a couple who were on the same carriage as the man said that he had a knife.
“They said he was shouting that he wanted to get into the driver’s carriage.”
The witness added that around four police cars and two riot vans were outside the station.
A spokesman for British Transport Police said: “We were called to Haddenham and Thame Parkway station shortly after 5pm following reports of an assault on a train guard.
“Our officers attended and a 23 year-old man was arrested at the scene on suspicion of ABH and is currently in custody awaiting interview.”
