AN ARMED robber threatened a shop keeper with a knife, assaulted him and then stole a large amount of cash this afternoon.

The robbery happened at Premier Stores in Booker Lane, High Wycombe, around 1.30pm, police said.

The shop-keeper suffered eye and facial injuries after the culprit forced him to open the automatic teller machine and attacked him.

The robber left on foot with the money, though officers said it is unknown how much was taken.

Police described the offender as a black man, in his mid twenties dressed in dark clothing with a dark blue scarf wrapped around his face.

It is believed another man, possibly an accomplice, waited outside the store during the robbery.

Witnesses are being sought and if you can help the investigation call Det Con Chris Mavers of High Wycombe CID via the 24-hour Thames Valley Police Enquiry Line on 101.

If you don't want to speak directly to the police you can contact the independent charity Crimestoppers anonymously on 0800 555 111 or online at crimestoppers-uk.org. No personal details are taken, information is not traced or recorded and you will not go to court.