A man was hit on the head and threatened with a knife in a robbery in Wellingborough at the weekend.
At about 3.45am on Saturday (August 5), the victim was walking along Knox Road.
He was hit to the back of the head by what is believed to be a concrete block and threatened with a knife.
The offender demanded his wallet and made off when it was handed over.
The man sustained cuts to the head which required hospital treatment and grazes to his hands and knees.
The offender is described as a stocky 5ft 6in white man, balding, with a small amount of hair on his chin and wearing glasses and a dark top.
Anyone who has information should contact police on 101 or Crimestoppers anonymously on 0800 555111.