Detectives are investigating a robbery in the park area of Providence Place, Brighton, shortly after midnight on Sunday (2 October).
A man in his mid 20s was walking with his girlfriend towards London Road, Brighton, via Providence Place and Ann Street when they were approached by a group appearing to consist of four young white men.
All were wearing dark coloured clothing with hoodies and all were described as tall, skinny and slim.
One threatened the victim with a glass bottle, forcing him to hand over his mobile phone and wallet. No one was injured.
Anyone who saw what happened or who may have other information is asked to email 101@sussex.pnn.police.uk or phone 101, quoting reference 6 of 02/10.
Alternatively they can contact the independent charity Crimestoppers on 0800 555 111 (www.crimestoppers-uk.org)
A 14-year-old boy from Brighton has been arrested on suspicion of robbery. After questioning he was bailed until Sunday, 30 October while enquiries continue.