A woman was punched in the back of the head in the early hours of the morning in Kettering.
The incident happened at about 2.20am on Sunday, September 21 in the Horsemarket area of the town, close to the bus shelters and taxi rank.
Police have released the information about the attack today (Tuesday, October 7).
A spokesman for Northamptonshire Police said: “It is believed a large group of people saw the assault and officers investigating the incident would like to speak to anyone who was in the area at the time.”
Witnesses can phone Northamptonshire Police on 101 or Crimestoppers on 0800 555111.