Police are keen to speak to a brave woman who intervened when she saw a gang of thugs assaulting a 17-year-old in Derbyshire.

Derbyshire Constabulary has released shocking CCTV footage of an assault on a teenage youth by a large group of men, which left the victim with a cut mouth, bruising and swelling to his head.

Officers are keen to trace anyone who was around St Peter's Street in Derby city centre at around 11pm on Thursday, June 29. Police would like to speak to the woman who prevented the victim from suffering further injuries, but are insisting that she is not a suspect.

In the footage, the unknown woman is seen stopping as she sees the attack taking place, before walking over to the gang and trying to pull members off the victim.

Detective Constable Nikita Devney said: "Since the incident, we have been working hard to identify suspects. We have now released CCTV footage of the incident and are asking for help to identify those involved.

"One of those highlighted in the footage is a young woman in a white dress. I need to stress that she is not suspected as being an offender; in fact she is instrumental in stopping the incident and tries hard to prevent the victim being subject of further assault.

"However, it seems clear that she may have information as to those involved and as such I would like to speak to her."

Anyone with information is asked to call DC Devney on 101 quoting reference number 17000275662 or through Crimestoppers, anonymously, on 0800 555111.