A silent march organised by the far-right Democratic Football Lads Alliance in central London has erupted into violent scenes.
Hundreds of supporters were walking from Park Lane to Whitehall, but some of them started to push through their police escorts.
Many could be heard chanting whose streets? Our streets? as they marched down Pall Mall.
Dozens could be seen fighting with officers, with one seen threatening a policeman and screaming Ill kill you, while several hostile-looking men had to be held back from joining in the fighting by their friends.
Scores of police on horseback and wearing riot gear tried to control the swelling groups with police vans trying to block them in.
A spokesperson for the Met Police told Metro.co.uk that one person has so far been arrested.
On Facebook, the march organisers had said they were protesting returning jihadists, thousands of Awol migrants, rape gangs and groomers, and veterans treated like traitors.
Meanwhile, police were deployed at Trafalgar Square to keep the Football Lads from a group of counter-demonstrators, including some who shouted Nazi scum, off our streets!