Dozens of youths engaged in mass gang brawl and shut down an entire shopping mall in Westfield, in East London.
The brawl broke out around 2:30 on St. Stephens Day and involved two rival gangs and a number of police.
Scotland Yard had granted special stop and search powers to police for several hours after the disturbances.
They later announced 11 arrests as well as the seizure of several blades, some of which were military grade combat knives.
Two police officers were also wounded in attempting to stop the brawl and were treated in Hospital for non-life-threatening injuries.