Police are appealing for witnesses after a 20-year-old woman was struck in the face, causing significant bleeding.
Police said the incident happened the A270 Lewes Road, Coldean, Brighton, close to Moulsecoomb Social Club, between 10pm and 11pm on Saturday, June 22.
A police spokesman said it is thought to have been witnessed by several people waiting at a nearby bus stop.
Another potential witness was a middle-aged woman, according to police, who got out of a white car parked nearby, and three young women and a man in another parked car, all of whom got out to go to the aid of the victim.
In doing so, the man was shouted at by the suspect, who was wearing a light salmon-coloured top with black jeans, police added.
Police said the victim, who has long blonde hair and who was wearing a black dress, suffered a suspected broken nose.
Crime investigator Ellie Benson said: “I would like to speak to any of the people mentioned or anyone else who may have seen what happened.”
They can contact police online or by phoning 101, quoting serial 47190094510. Alternatively, they can contact the independent charity Crimestoppers anonymously online or by phoning 0800 555 111.
A police spokesman added: “A 22-year-old Brighton man has since been arrested on suspicion of assault and currently remains in police custody.”