A man found unconscious near Brighton Town Hall with a broken skull early remained critically ill last night.
The 22-year-old has a severe fracture and is on life support at the Royal Sussex County Hospital in Brighton.
Detective Inspector Bill Warner said: "We are still not positive about his identity but we are making progress."
The man is slim with dreadlocks, a thin beard, moustache and long sideburns. He wore a green army-style jacket and jeans.
Anyone with information should call Brighton CID on 0845 6070999.
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