The leader of an anti-monarchy group, who was among 52 people arrested on the day of the king’s coronation, was released after nearly 16 hours in police custody.
Graham Smith was released by Met Police around 11pm on Saturday while the majority of his fellow Republicans remained detained.
In a post on Twitter, Mr Smith said there was “no longer a right to peaceful protest in the UK”.
“I have often been told that the monarch is there to defend our freedoms. Now our liberties are being attacked in his name.”
The Metropolitan Police have been heavily criticized for the arrests, with some campaign groups comparing the “incredibly alarming” arrests to “something you would expect in Moscow and not London”.
The force confirmed 52 people had been arrested on charges of brawling, public order offences, breach of the peace and conspiracy to cause a public nuisance around the coronation.
Metropolitan Police Commander Karen Findlay acknowledged concerns about arrests of protesters but defended Scotland Yard’s actions, saying: “Our duty is to do so in a reasonable manner, in accordance with relevant legislation.”
Also arrested on Saturday were members of Just Stop Oil and Labor for a Republic.
The Met said it received information that protesters were “determined” to disrupt the coronation – including defacing public monuments with paint, breaching barriers and disrupting official movements.
However, activists said the protests had been “peaceful” and called the arrests “a dangerous precedent for us as a democratic nation”.
The force confirmed reports from Just Stop Oil that 13 protesters were arrested on The Mall and six were arrested for public nuisance on St Martin’s Lane following Republic protests.
Three people were also arrested in Soho, three at Wellington Arch and five in Whitehall for conspiring to cause public nuisance and another in Whitehall was arrested for religiously aggravated conduct likely to cause nuisance.
The Met said a further 14 people have been arrested in east London on suspicion of conspiracy to cause a public nuisance.
Footage from the Mall showed the Just Stop Oil protesters being handcuffed and taken away by a heavy police presence.
Animal Rising said some of its supporters were arrested at a training session “miles from the coronation” on Saturday.
Nathan McGovern, spokesman for the campaign group, described the arrests as “nothing short of a totalitarian crackdown on freedom of expression and all forms of dissent”.
Human Rights Watch called the arrests “incredibly alarming,” adding, “You would expect that in Moscow, not London.”
Amnesty International’s chief executive, Sacha Deshmukh, also raised concerns after police reportedly received orders to arrest people with megaphones.
Separately, Westminster Council’s cabinet member for Communities and Public Protection Aicha Less said she was “deeply concerned” by reports of arrests of members of his volunteer team, the Night Star, who help vulnerable people on the streets late at night.
“We are working with the Metropolitan Police to determine exactly what happened and in the meantime we are in touch with our volunteers to ensure they get the support they need,” she said.