Video report by ITV News Correspondent Dan Rivers
Several officers have been injured after anti-Covid lockdown protesters clashed with police.
A group of around 100 demonstrators threw cans and bottles at police in London's Hyde Park as they were urged to go home.
Earlier in the day, thousands marched through the streets of the capital carrying placards with slogans such as "Fear Westmonster not the virus" and "Stop destroying our kids' lives", while others argued the restrictions designed to reduce transmission of the deadly disease are anti-free speech.
The Metropolitan Police said 36 people had been arrested, the majority for breaching coronavirus restrictions.
While most demonstrators dispersed after the march finished, around 100 returned to Hyde Park where they threw bottles and cans at police, forcing them to retreat to their vans.
They then chased, kicked and punched police vehicles.
Around a hundred police officers wearing riot helmets and carrying shields then arrived and urged people to go home.
Members of the public left the park, with small children carried by their parents.
The march came despite police warnings to avoid demonstrations due to Covid-19 restrictions and the banning of meeting up outdoors with more than one other person, in England.
The majority of the protesters did not appear to be following social distancing measures or wearing masks as the made their way through the streets of the capital from Hyde Park to Westminster.
The march was organised to mark one year since the first Covid restrictions were put in place.
Responding to the protests, Deputy Assistant Commissioner Laurence Taylor said: “This was another challenging day for our officers and I would like to thank them for their professionalism.
“Throughout the day, officers sought first to engage with people who had gathered to explain that their actions were unlawful under the Covid-19 regulations, and encouraged them to go home to help protect themselves and others during this public health crisis.
“Where this approach did not work and officers were met with hostility, police enforced the regulations and made arrests.
“We once again saw police come under fire from missiles thrown by people in crowds, and several were injured as a result of targeted assaults.
"It is totally unacceptable and saddening that officers enforcing regulations that are there to protect us all were the victims of violent attacks. I wish them a speedy recovery.
“Many of those on duty in central London today should have been in their local communities dealing with violent crime and other local issues, but they played a role in reducing the risk of Covid-19 spreading by dispersing crowds.”
It comes as the government is facing renewed pressure to ease Covid lockdown restrictions to allow protests to go ahead.
More than 60 MPs and peers have signed a letter warning that allowing the police to criminalise people for protesting is "is not acceptable and is arguably not lawful".
The letter to Home Secretary Priti Patel and Health Secretary Matt Hancock was co-ordinated by Liberty and Big Brother Watch.
Signatories include the Tory MPs Sir Charles Walker, Steve Baker, Sir Christopher Chope and Sir Desmond Swayne and the Liberal Democrat leader Sir Ed Davey.
It follows the outcry over the way the Metropolitan Police moved in to break up a vigil last week on Clapham Common in memory of Sarah Everard.
Footage shows police arresting a woman and clashes between officers and mourners
The letter said such "shocking scenes" were "entirely avoidable" if the government had provided guidance to police and ensured protests were clearly exempt from the ban on gatherings under lockdown.
Sam Grant, head of policy and campaigns at Liberty, said: "In a healthy democracy, protest is a critical way we can fight for what we believe in.
"The government's current quasi-ban on protest is completely unacceptable.
"Last week, the police conceded protest is not banned under the lockdown regulations, but used them to threaten then arrest demonstrators anyway.
"The home secretary must immediately issue guidance to all police forces to ensure socially distanced protests can go ahead and create an explicit exemption for protest in the current regulations."
Meanwhile in Brixton, protesters gathered in a more socially distanced manner to take part in an anti-racism rally - part of a worldwide protest which has seen more than 20 countries link up online - livestreaming the events in their cities.
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