Police have been heavily criticised over the “incredibly alarming” arrests of Republican protesters ahead of the King’s coronation.
Campaign groups said Saturday’s arrests, including that of the chief executive of anti-monarchy group Republic, were “something you would expect to see in Moscow, not London”.
Just after 7am, footage of Republic chief executive Graham Smith was posted on Twitter which showed him among the demonstrators apprehended on St Martin’s Lane near Trafalgar Square.
In one video an officer said: “I’m not going to get into a conversation about that, they are under arrest, end of.”
Just Stop Oil told the PA news agency approximately 13 protesters were arrested on the Mall ahead of the coronation.
A spokeswoman for the campaign group said five demonstrators were also arrested at Downing Street and one at Piccadilly.
Footage from the Mall showed the Just Stop Oil protesters being handcuffed and taken away by a heavy police presence.
The force also said they made a number of breaching-the-peace arrests in the area of Carlton House Terrace and a further three arrests in the Wellington Arch area on suspicion of possessing articles to cause criminal damage.
Animal Rising said a number of their supporters were apprehended on Saturday while at a training session “miles away from the coronation”.
Nathan McGovern, spokesman for the campaign group, described the arrests as “nothing short of a totalitarian crackdown on free speech and all forms of dissent”.
Human Rights Watch labelled the arrests “incredibly alarming”, adding: “This is something you would expect to see in Moscow, not London.”
Amnesty International’s chief executive Sacha Deshmukh also raised concerns after police were reportedly given instructions to apprehend people with megaphones.
Outside London hundreds of people joined a march through Cardiff city centre in protest against the monarchy as the King was crowned.
Demonstrators walking down Queen Street shouted “Down with the Crown, not my King” and “God save the poor”.
Nick Wall, member of campaign group Republic and chairman of the Labour For Republic organisation, addressed crowds at a Not My King rally in Cardiff where he called the arrests of protesters in London “disgraceful”.
“I felt compelled to say a few words because one of Republic’s co-ordinators, his name is Ben and he’s only 21 years of age, and he’s been arrested. It’s appalling.”
After the King was officially crowned, the Met tweeted to say: “We swear that we will pay true allegiance to his Majesty, and to his heirs and successors according to law.”
One Just Stop Oil protester Ben Larsen, 25, said he was there to see the coronation and peacefully protest.
Grinning at police officers, he told them: “You’ve searched me and haven’t found shit.”
On Wednesday the Met said they would have an “extremely low threshold” for protests during the coronation celebrations, and that demonstrators could expect “swift action”.
Under the controversial new Public Order Act, protesters who have an object with the intention of using it to “lock on” are liable to a fine, with those who block roads facing 12 months in prison.
Critics previously hit out at plans from the Met to use facial recognition software on crowds to assist their policing operations.
An official letter warning of the new powers was sent to Republic, which said its campaign around the coronation would proceed as planned.
Just after 7.30am on Saturday, one woman in a Republic T-shirt was carried away by officers during an interview with the PA news agency.
Before being arrested, she said: “We had a delivery of placards ready for the protest and then the tactical support unit questioned us as to how we had got through the road closures.
“They questioned whether what we were doing was a delivery.
“They then said they found evidence of means of locking on, of items that could be used to lock on, and they arrested us.”
Another protester, Symon Hill, 46, who was previously arrested for shouting “who elected him?” during a proclamation ceremony for the King, said he hoped he would not be arrested again.
Mr Hill had charges against him of using threatening or abusive words or disorderly behaviour likely to cause harassment, alarm or distress dropped by the Crown Prosecution Service.
He told PA: “‘I very, very much hope I will not be arrested. I am joining peaceful, lawful protest and I am worried there will be more arrests on spurious grounds.”