Police are hunting a gang who smashed their way into ticket vending machines at railway stations, causing more than £100,000 worth of damage.
British Transport Police (BTP) have released dramatic footage of the offences taking place, with the gang using angle grinder cutting equipment and pickaxes to steal more than £3,000.
BTP have also published images of three men who are currently their main suspects.
The raids have been at stations across north London and Hertfordshire.
Detective Constable Nick Thompson, who is leading the investigation, said: "I am now confident this spate of thefts is the responsibility of the same gang of three men.
"They target smaller stations in the early hours when there are no staff on duty and the last train has gone. They arrive as a group, head straight to the automatic ticket vending machines and set about a sustained attack using heavy-duty cutting equipment and pick axes."
He went on: "The dramatic CCTV video shows the men in action, attacking the ticket machines with an angle grinder and forcing the front open to get at the cash boxes inside.
The first reported incident took place just after midnight on April 19, at Brookmans Park station,
Hertfordshire. After tampering with security cameras, the gang managed to break open the front of the ticket machine and got away with £750 in cash. Their actions caused more than £23,000 worth of damage.
This was followed by an attack two days later at nearby Bayford railway station. Despite again causing more than £23,000 worth of damage to the machine, this time the gang left empty-handed as they targeted a machine which only accepted card payments.
Three weeks later two stations were targeted on the same night, with ticket machines at Watton-at-Stone in Hertfordshire and Oakleigh Park in north London attacked in the early hours of May 18.
The gang got away with more than £900 in cash from the two machines and caused an estimated £30,000 worth of damage.
Hadley Wood station in north London was targeted the following morning. Here the gang caused more than £23,000 worth of damage and stole £650 in cash. The last known attack was on May 23 at Welham Green station in Hertfordshire, where £850 was stolen and £7,000 worth of damage was reported.
DC Thompson added: "The money stolen in these attacks really does pale into insignificance when you consider the cost of the damage - which is estimated as 33 times the value of the cash taken.
"These thefts haven't just hit the rail industry financially, they've also caused disruption and inconvenience to passengers, with ticket machines taken out of service for repairs."
Anyone with information is asked to contact BTP on 0800 40 50 40, or text 61016, quoting reference ESUB/B9 of 04/06/2014. Information can also be passed anonymously to the independent charity Crimestoppers on 0800 555 111.