Officers have also released CCTV images of a man they want to identify and speak to in connection with the incident, which took place on Monday, 12 July 2010.

PC Jason Weatherman, the investigating officer, said the theft took place at around 4.20pm in the Co-Op store on the approach to the station:

“The thief entered the store alone and empty-handed. Shortly after entering, he took some food items from shelves and placed them down his trousers.

“After doing so, he tried to leave the store without making any attempt to pay for the goods.”

A vigilant member of staff approached the man and asked that he return the goods, at which point the man produced a grey lock knife with a six-inch blade and threatened to stab the shop assistant.

Fearing for her safety, the shop assistant let the man past and he subsequently made off out of the shop.

PC Weatherman added: “Any theft or attempt at theft is unacceptable and the fact that this man produced a weapon for the sake of getting some free food is shocking.

“If you recognise the man, or have any more information regarding the incident, I urge you to contact police.”

Anyone with any information about the incident should ring British Transport Police on Freefone 0800 40 50 40, quoting reference 360 of 12/07/2010, or call Crimestoppers, anonymously, on 0800 555 111.