A gang of teenagers attacked a 21-year-old man on Brighton seafront as he was walking home.
Sussex Police said: “The victim was assaulted in King’s Road at about 11.15pm on Monday (3 November) near to the King’s Hotel.
“He suffered serious head injuries including a suspected broken cheekbone after he was punched and kicked to the ground.
“The attackers ran off when another man stepped in to help the victim.”
Detective Constable Duncan Lloyd said: “This was a sustained and unprovoked assault by a group of teenagers on an innocent member of the public.
“Had it not been for the selfless act of a passer-by, the victim would have undoubtedly received more severe injuries.
“We need to speak to anyone who was in the area and saw or heard any of what happened.”
A 16-year-old girl from Southwick, a 15-year-old boy from Horsham and a 17-year-old boy from Seaford were arrested on suspicion of assault.
They were questioned before being released on bail until Wednesday 7 January.