A 22-year-old man was knocked unconscious and spent two days in hospital after he was punched in the head in a Northampton pub garden.
The man was assaulted in the beer garden of The Old Bank pub in St Giles Square, Northampton, on Friday at about 11.30pm.
The victim had intervened in an altercation his friend was having with another man, and was then hit in the back of the head by another person, causing him to fall unconscious.
He was hospitalised for two days with a head injury, which officers investigating the incident said could have been much worse, and they are appealing for those who witnessed the incident, which happened on a busy Friday night, to contact police.
Witnesses, or anyone with information, are asked to call Northamptonshire Police on 101.
Alternatively, they can call the independent charity Crimestoppers anonymously on 0800 555 111 or use the anonymous online form at www.crimestoppers-uk.org.