A man was taken to hospital with head injuries following an incident in Northampton town centre in the early hours of Saturday.
The 53-year-old man was found injured in the street by passers-by who stopped to help and call the emergency services.
A police spokesman said: “A 53-year-old man was taken to Northampton General Hospital following an altercation in Abington Street.
“It happened outside Marks & Spencer at about 1am on Saturday, April 18.
“He had head injuries but they were not life-threatening.”
Any witnesses to the assault are asked to call police on 101.