Today they released CCTV image of a man they would like to speak to in connection with the incident in Halifax in the early hours of Sunday, November 27.
A 19-year-old man was assaulted on Commercial Street, close to the junction of Silver Street, at around 5am.
Detective Constable Jason Mohan of Calderdale CID said, "We would like to speak to the man on the left on the CCTV and would appeal to anyone who can help us identify him to come forward.ã€€
"I would also appeal to the other people in the CCTV to come forward as it is possible they may have vital information about the incident."ã€€
Anyone with information is asked to call Det Con Mohan at Calderdale CID via 101, quoting 13160713628.
Information can also be anonymously to Crimestoppers on 0800 555 111.