Protesters forming the “Unite the Kingdom” rally gathered in the centre of the capital, holding Union and St George’s flags.
They heard a series of speeches, including from Mr Robinson, who called it the “biggest freedom of speech” in British history.
Police estimated that between 110,000 to 150,000 attended the event, significantly exceeding the estimates of organisers.
An anti-racism counter-protest, attended by about 5,000 campaigners, also took place, with the two groups clashing on Whitehall and Trafalgar Square, separated by lines of police.
There were 25 arrests made, with many more likely, the Metropolitan Police said, adding that officers faced “significant aggression” from “Unite the Kingdom” attendees.
“The violence they faced was wholly unacceptable,” police said.
“26 officers were injured, including four seriously – among them broken teeth, a possible broken nose, a concussion, a prolapsed disc and a head injury.”
Police said the Robinson crowd was too big to fit into Whitehall and confrontation happened when police tried to stop them from encircling counter-protesters and accessing the area from different routes.
A spokesman said: “When officers moved in to stop them, they faced unacceptable violence. They were assaulted with kicks and punches. Bottles, flares and other projectiles were thrown.
“Nine arrests have been made so far for various offences, but many more people have been identified as committing offences. We will find them and they will face police action, even if it is not possible to do so today.
“Officers are continuing to face aggression in multiple locations, in particular at the north of Whitehall as they work to create a safe exit route for those who have been taking part in the Stand Up To Racism protest.”
Home Secretary Shabana Mahmood condemned “those who have attacked and injured police officers” during the protests, promising anyone taking part in criminal activity will “face the full force of the law”.
Musk makes surprise appearance
Robinson live-streamed the rally on X, with its audience peaking at 2.9 million viewers on Saturday afternoon.
Making a surprise appearance via video link, tech billionaire Elon Musk called for a “change of government” in the UK.
“You can’t – we don’t have another four years, or whenever the next election is, it’s too long,” Musk told the crowd. “Something’s got to be done. There’s got to be a dissolution of parliament and a new vote held.”
TV presenter Katie Hopkins also spoke after earlier appearing alongside Robinson, Lawrence Fox and Ant Middleton at the front of the march.
‘Revolution has started – you can’t stop it’
With a voice which sounded hoarse from shouting, Robinson told crowds during his speech that “millions” had showed up for the rally.
“The dam has well and truly burst,” he said. “The cat is out of the bag and there is no putting it back in. The silent majority will be silent no longer.”
Addressing Sir Keir Starmer and the Labour government, Robinson said: “The revolution has started – and you can’t stop it.”
Referring to a Court of Appeal decision to overturn an injunction blocking asylum seekers being housed at The Bell Hotel in Epping, Essex, Robinson claimed UK courts found the rights of undocumented migrants supersede those of the “local community”.
He said: “They told the world that Somalians, Afghanis, Pakistanis, all of them, their rights supersede yours – the British public, the people that built this nation.”
