(London) British police released on Saturday evening the main organizer of an anti-monarchy demonstration on the sidelines of the coronation of Charles III, whose arrest had been widely criticized, the organization Republic reported.

The Republican movement said late Saturday night that its director Graham Smith and several other members were released from police custody after about 16 hours of detention, saying their phones had been confiscated.

“The right to protest no longer exists in the UK,” Graham Smith tweeted. “I have often been told that the monarch serves to defend our freedoms, now our freedoms are under attack in his name.”

Six activists were arrested early Saturday morning as they prepared to demonstrate in Trafalgar Square, on the route of the procession leading the king to Westminster Abbey. Hundreds of “Not my King” signs were also seized, according to Republic.

Hundreds of supporters of the organization were however able to demonstrate calmly, booing as the king and queen passed by.

The arrests are among 52 arrests made by police on the sidelines of the coronation, in addition to dozens of environmental activists known for their heavy-handed actions blocking traffic and disrupting public events.

They have been criticized by opposition politicians and human rights organizations.

They came as a controversial new law, enacted days before the coronation, boosts police powers to counter protests. The text allows arrests on the grounds of a simple intention to disturb public order.

The Metropolitan Police of London (“Met”), which had deployed more than 11,000 officers on Saturday, defended themselves on Saturday evening, saying they had “received information indicating that protesters wanted to disrupt the coronation procession”.

“We have a duty to intervene when demonstrations turn criminal and risk causing serious disruption,” said Karen Findlay, who coordinated the police operation, quoted in the police statement.

“It depends on the context. The Coronation is a once-in-a-gen event and it’s a key part of our assessment,” she added.

Fueling criticism of the Met, weakened by a series of scandals implicating it for racism and misogyny, its agents have also arrested volunteers distributing rape alarms to women, believing that these devices could be used to scare horses during the coronation.