Met police detectives are investigating a bottle attack on a policeman in Lambeth.
The officer had been called to a bar in Clapham Road in January after reports of trouble between security door staff and a group of young men.
He was taking statements and had a bottle thrown at his head when trying to make an arrest.
He needed hospital treatment for a head injury.
The police made some arrests.
But they have released an image of another person they want to speak to.
DC Rich Mosford of Lambeth CID, said:
This was a serious assault on a police officer who suffered a head injury and was left bloodied by a glass bottle deliberately thrown at him as he tried to bring some order to the situation.
The consequences could have been far worse. Attacks on officers of this nature and severity are thankfully rare and they will not be tolerated.
I would like to praise the officer involved who, after sustaining his injury, still managed to keep hold of and detain a potential suspect amidst the disorder.
Anyone has information is asked to call 0208 649 2134 or 101 quoting CAD 291/7Jan, or Crimestoppers anonymously on 0800 555 111.