A 17-year-old boy was stabbed during a brawl in Clapham Common which saw police arrest nine youths at a chaotic 'unauthorised gathering'.
The 'Clapham Court Connect', a heavily promoted event held on May 22, spiralled out of control after a boy suffered multiple stab wounds in a fight.
Hundreds of young people headed to Clapham Common to celebrate the start of the May school half-term from '4pm till late'.
But the fun and sun was short-lived as the Metropolitan Police descended on the event to disperse the crowds and break up the brawl.
Footage of the fight shared on social media showed a group of youths viciously attacking one another, with one young person wearing a grey tracksuit being beaten to the ground.
Police officers then pushed through the crowds, chasing down those responsible to make arrests.
Other videos showed swathes of police officers running after young people with batons, pinning suspects to the floor and being surrounded by crowds of teenagers.
One shot showed the navy-coloured Territorial Support Group police vehicles stationed across Clapham Common to handle the unruly crowds.
A crowd of youths attending the 'Clapham Common Connect' erupted into a vicious brawl on May 22
Following the fight, nine young people were arrested - including a 20-year-old and a 15-year-old for possessing a knife
In another video, two medics wheeled away a person strapped to a stretcher under a yellow blanket, while another video filmed at night showed emergency services gathered around a yellow canvas being dragged away.
Following the fight, the 17-year-old was taken to hospital, where his condition was said to be 'neither life-changing nor life-threatening.'
Nine arrests were made in total. They included a 20-year-old man and a 15-year-old boy for possession of a knife; two boys, 14 and 16, for grievous bodily harm and affray; an 18-year-old for assaulting a police officer; and four boys, one aged 16, two 17 and one 19 for affray.
The chaos in Clapham continued long after sundown with police and ambulance teams still present into the night.
Rum punch was reportedly being sold during the event despite most attendees being underage.
The gathering was promoted by Greasy Events which boasted 'good vibes, bad behaviour' on TikTok. The founder has been approached for comment.
A Metropolitan Police spokesperson said: 'We were called on Friday, 22 May to an unauthorised gathering on Clapham Common.
'The group were dispersed by officers after fighting broke out in the crowd, following this we made nine arrests.
'A 17-year-old boy was taken to hospital after he was found suffering with stab wounds. His injuries were assessed as neither life-changing nor life-threatening. All of those arrested remain in police custody.
'We urge anyone who was at the event or who has any information to come forward to police by calling 101 and quoting CAD8948/22May.
'A police presence will remain in the area, and we'll be reviewing CCTV and other evidence in the coming days.'
All those arrested remain in custody, the Metropolitan Police said.