Police in Crawley are looking for a man who is believed to have witnessed an incident where a woman was sexually assaulted in Broadfield Barton.
The woman, in her early thirties, was outside the shops at about 11.15pm on 16 August.
The police are solely looking for this man as a witness.
Another man, aged 37, was arrested on suspicion of sexual assault and causing actual bodily harm, he has been released on bail while enquiries continue.