A man suffered a fractured skull in an unprovoked attack in Hove as he walked to work early on Saturday morning.
Detectives are appealing for witnesses and information about the attack, which also left the man, who is in his early 40s, with a cut above his eye.
The attack happened at about 5.30am on Saturday in Church Road, Hove.
The victim was approached by a man walking from the direction of Second Avenue.
The attacker asked the victim for a light before punching him to the ground.
The offender was described as white, 5ft 11in to 6ft tall, of stocky build, with short dark hair. He wore a full-length overcoat which covered most of his lower legs.
Brighton detectives are investigating and asked anyone who either witnessed the incident or has information about it to call Sussex Police on 0845 6070999.