A man was hit on the head during an unprovoked attack as he walked through a Wellingborough park.
The 23-year-old was assaulted as he walked through Castle Fields Park on Saturday (April 16).
The man was walking through the park between 7pm and 7.30pm when he felt a blow to the head and fell to the floor.
Three people riding bikes then went past him. One was wearing a black jacket with grey/black jogging bottoms. There is no description of the other cyclists.
Officers would like to speak to anyone who may have witnessed this incident or who may have any information regarding it.
Witnesses can contact police on 101 or Crimestoppers anonymously on 0800 555 111.