Several officers were punched, kicked and struck by bottles tossed by people at the fringes of the Unite the Kingdom rally, Metropolitan Police said.
Reinforcements with helmets and riot shields were deployed to support the 1000-plus officers on duty.
Twenty six police officers were injured — four who were seriously hurt, including broken teeth and a concussion, a possible broken nose and a spinal injury.
At least 25 people were arrested for offences including violent disorder, assaults and criminal damage, and the investigation continues, police said.
Assistant Commissioner Matt Twist said police faced a "wholly unacceptable" level of violence.
"There is no doubt that many came to exercise their lawful right to protest, but there were many who came intent on violence. They confronted officers, engaging in physical and verbal abuse and making a determined effort to breach cordons in place to keep everyone safe," he said.
The rally drew an estimated crowd of between 110,000 and 150,000 people, far surpassing expectations, police said.
The rival March Against Fascism protest organised by Stand Up To Racism had about 5000 marchers.
Twist warned that more arrests are likely.
"Our post-event investigation has already begun - we are identifying those who were involved in the disorder and they can expect to face robust police action in the coming days and weeks," he said.
While the crowd was large, it fell far short of the one of the biggest recent marches when a pro-Palestinian rally drew an estimated 300,000 people in November 2023.
Robinson, whose real name is Stephen Yaxley-Lennon and is known for his nationalist and anti-migrant views, billed the march as a demonstration for free speech, and also said it was in defence of British heritage and culture.
The marches come at a time when the UK has been riven by debate over migrants crossing the English Channel in overcrowded inflatable boats to arrive on shore without authorisation.
Numerous anti-migrant protests were held in recent months outside hotels housing asylum-seekers following the arrest of an Ethiopian man who was later convicted of sexually assaulting a 14-year-old girl in a London suburb.
Some of those protests became violent and led to arrests.
Robinson had planned a Unite the Kingdom rally last October, but couldn't attend after being jailed for contempt of court for violating a 2021 High Court order barring him from repeating libellous allegations against a Syrian refugee who successfully sued him.
He previously served jail time for assault and mortgage fraud.
Robinson founded the nationalist and anti-Islamist English Defence League and is one of the most influential far-right figures in Britain.
He urged followers not to wear masks, drink booze or get violent.
With PA
