A young woman was punched in the face for no apparent reason by a man on Thursday evening.
She was sitting near the Park lake and had chatted to the suspect at 6pm.
Det Insp Bardell said: “The suspect struck up a conversation and has then walked round the lake, approached her again and struck the victim in the head.”
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A witness chased after the man but was unable to keep up with him.
The suspect is described as black, six foot tall and was wearing ripped light blue jeans and a black top with a burgundy-coloured scarf.