A man was left with concussion after another man allegedly punched him in the head on Monday night in St Clement.
Police are appealing for information regarding the incident, which took place near the Maupertuis pumping station at around 21:15.
The suspect is believed to have been walking a small white dog in the area before the “unprovoked attack”.
He is alleged to have punched the victim in the head, leaving him with a concussion.
The two men, both in their 40s, are believed to know each other.
Police are particularly keen to speak to a female driver of a Ford Focus who is said to have intervened and encouraged the men to separate.
Anyone with information has been asked to contact police on 612612 quoting M05575/2025.
They can also make an anonymous report through the charity Crimestoppers on 0800 555 111 or online at crimestoppers-uk.org.