Within minutes, police began arresting the demonstrators, as bystanders chanted “Shame on you” and “Met Police, pick a side, justice or genocide.”

There were some scuffles and angry exchanges as officers dragged away demonstrators who went limp as they were removed from the crowd.

Eight hours after the protest started, police said they had arrested more than 425 people, more than 25 of them for assaulting officers or public order offenses and the rest under the Terrorism Act.

“In carrying out their duties today, our officers have been punched, kicked, spat on and had objects thrown at them by protesters,” said Deputy Assistant Commissioner Claire Smart, who called the abuse directed at police “intolerable.”

Defend Our Juries said aggression had come from police officers and dismissed claims that protesters had been violent as “frankly laughable.”

More than 700 people were arrested at earlier protests, and 138 have been charged under the Terrorism Act.

Mike Higgins, 62, who is blind and uses a wheelchair, was arrested last month but returned to demonstrate on Saturday.

“And I’m a terrorist? That’s the joke of it,” he said. “I’ve already been arrested under the Terrorism Act and I suspect I will be today.

“Of course I’ll keep coming back. What choice do I have?”

The government proscribed Palestine Action in July after activists broke into a Royal Air Force base and vandalised planes to protest against what they called Britain’s support for Israel’s offensive against Hamas in Gaza.

The activists sprayed red paint into the engines of two tanker planes and caused further damage with crowbars.

Proscription made it a crime to publicly support the organisation. Membership of, or support for, the group is punishable by up to 14 years in prison.

Palestine Action has carried out direct action protests in the UK since it formed in 2020, including breaking into facilities owned by Israeli weapons manufacturer Elbit Systems UK, and has targeted other sites in Britain that participants believe have links with the Israeli military.

The group has targeted defence companies and national infrastructure, and officials say their actions have caused millions of pounds in damage that affect national security.

Banning the group, then-Home Secretary Yvette Cooper said, “The assessments are very clear, this is not a nonviolent organisation.”

Palestine Action has won approval from the High Court to challenge the ban, a ruling the government is seeking to overturn. The case is ongoing, with a hearing scheduled for Sept. 25.

Supporters say the ban stifles free speech

The UN human rights chief has criticised the British government’s stance, saying the new law “misuses the gravity and impact of terrorism.”

The decision to designate Palestine Action as a terrorist group “raises serious concerns that counterterrorism laws are being applied to conduct that is not terrorist in nature, and risks hindering the legitimate exercise of fundamental freedoms across the UK,” Volker Türk warned.

He added that according to international standards, terrorist acts should be confined to crimes such as those intended to cause death or serious injury or the taking of hostages.

Huda Ammori, Palestine Action’s co-founder, has condemned the government’s decision to ban it as “catastrophic” for civil liberties, leading to a “much wider chilling effect on freedom of speech.”

The group has been supported by prominent cultural figures including bestselling Irish author Sally Rooney, who said she planned to use the proceeds of her work “to keep backing Palestine Action and direct action against genocide.”

Israel – founded in part as a refuge in the wake of the Holocaust, when some 6 million European Jews were murdered – vehemently denies it is committing genocide.

Britain’s government stressed that proscribing Palestine Action as a terrorist group does not affect other lawful groups – including pro-Palestinian or pro-Israel voices – campaigning or peacefully protesting.

About 20,000 people, by a police estimate, attended a separate pro-Palestinian march in London.