Police are appealing for witnesses following an assault in Montague Street, Worthing, around 1.55pm on Saturday, October 22.
A man was reported to have been struck across the head with a glass bottle by another man outside Marks and Spencer.
The victim was taken to hospital by colleagues from SECAmb with injuries to his head and ear.
It is believed the two men are known to each other.
When officers attended the scene, members of the public restrained a man who may have information which could help them with their enquiries.
A 35-year-old man was arrested on suspicion of GBH with intent and remains in police custody.
Anyone with video footage from the incident or people who witnessed what happened are asked to report it to police online or call 101 quoting serial number 582 of 22/10.