A fight between two men in the early hours of Sunday morning (5 February) left one of them in hospital with a broken nose and cuts to his face.
It occurred just after 2am in the alley between Thompson Estates and the Pierson pub - it is not thought the men knew each other.
The injured individual was accompanied by a woman and was wearing an athletic three-quarter zip top with dark jeans and white trainers.
The other man was with another male - both described as being in their early 20s.
One of them was wearing a white polo shirt, dark blue jeans, a black body warmer and black trainers.
An 18-year-old man was arrested later on Sunday 5 February on suspicion of grave and criminal assault - he has since been released on bail.
Anyone who may have some information is asked to contact the police on 612612.
Alternatively, the charity Crimestoppers can be called anonymously on 0800 555 111.
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