An 18-year-old man has been arrested on suspicion of assault by police in Preston.
A man in his early 20s is recovering in hospital after being assaulted outside the Rumes night club after a Boxing Day night out.
The victim was leaving the Church Street venue when he is believed to have been punched, he then fell and hit his head.
The incident took place in the early hours of Friday morning.
Det Sgt John Crichton of Preston CID said: “This is understood to have been an unprovoked attack outside a busy nightclub, We will deal with it robustly.”
Anyone with information is asked to call Lancashire Police on 101.