A man was punched and robbed during an attacked in the Market Square in Northampton.
The victim was walked through the town centre at about 12.15am on Saturday and noticed a group of about five people.
One of the men in the group shouted verbal abuse and ran towards him.
The victim ran off but the offender caught up with him in Market Square and grabbed him, ripping his shirt and breaking his neck chain.
The offender punched the victim, causing him to fall, and stole his wallet.
Passers-by intervened and the offender ran off towards the Moon on the Square pub. He is described as white, with ginger hair and wearing blue jeans and brown shirt.
Witnesses to the incident, or anyone with information, are asked to contact Northamptonshire Police on 101. Alternatively, they can call independent charity Crimestoppers anonymously on 0800 555111.