A man's jaw was broken when a vicious fight erupted in broad daylight last Thursday.
The victim and his friend were in an alleyway behind The Bell pub, just off Hounslow High Street, when the tussle began at about 6.30pm.
A gang of up to 20 youths, mostly in their late teens and black or Asian, punched and kicked the 19-year-old to the ground.
One man was arrested at the scene but police are still seeking witnesses.
Anyone with information should call Hounslow CID on 020 8247 6133.