Police want to hear from anyone who was in the Queens Road/Queens Avenue area of Bristol between 3am and 3.35am on Sunday 30 January and witnessed an assault taking place.
A man in his 30s was assaulted by four unknown males outside Café Nero, causing him to temporarily lose consciousness.
He suffered significant facial injuries which required hospital treatment.
Another man was also assaulted while trying to assist the victim and suffered minor injuries.
Police would like to hear from anyone who witnessed the incident and can help provide a description of the offenders or any other information.
If you can help, please call 101 quoting reference 5222023841.
No personal details are taken, information cannot be traced or recorded and you will not go to court or have to speak to police when contacting Crimestoppers.