Passengers were forced to break out of Sutton rail station after staff closed it for the night before the last train arrived.
Pictures of the scene show people holding up the shutters as scores of people make a bid for freedom.
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An estimated 100 passengers were on board the train from London Victoria when it terminated in Sutton at about 1.30am on Sunday.
One passenger, Harry Nelson, said he joined a few others in forcing the shutters open.
Speaking to the Sutton Guardian, he explained: "I was on the last train back to Sutton and got off the train along with perhaps 100 other people. The ticket barriers were open but the shutters were shut.
"People starting heading to the second exit, which we thought may have been open, but we noticed people were turning away from that as well.
"There was kind of an air of panic as we realised we were trapped in the station.
"A few of us took the initiative to force open the shutters and break out. It took about five or six of us to get our hands underneath and just force it upwards.
Harry said he did not see a member of staff, but a spokesman for Southern, which manages Sutton station, said a member of staff had been at the station checking everybody had got off the train.
He said the train was not normally scheduled to stop at the station so staff had closed the shutters.
According to the Metro, he added: "Unbeknownst to passengers, a member of staff was on duty at the time, ensuring that the train they came in on was empty of passengers in order to return to the depot.
"The shutters had been closed at the end of the normal day's service, but the later train was an unexpected arrival so a staff member went to attend to the train as soon as it arrived.
"It's not a case of there being nobody around and the staff had gone home and left people shut in there."
He said the shutters had not been damaged and were locked again by staff after passengers had left.