Dozens of protesters have been arrested outside the Supreme Court ahead of a hearing challenging the ban on Palestine Action.
The Metropolitan Police said officers took action against 25 people on suspicion of expressing support for a proscribed organisation.
The demonstrators were holding placards with the same wording as an X post written by journalist and author Sarah Helm, the wife of national security adviser Jonathan Powell.
In October Ms Helm posted on X: "God help us authors who support Palestine and Palestine Action."
Her post faced scrutiny from the Metropolitan Police, as Palestine Action is banned as a terrorist organisation, but the force said it did not meet the criminal threshold and no further action would be taken.
The protesters had inserted different words instead of "authors" on their signs, including "normal people", "students" and "sons of Holocaust survivors".
The final protester to be arrested held a placard reading: "God help us who are not married to the UK's national security adviser who support Palestine and Palestine action."
As she was arrested, the woman shouted "Sarah Helm had the same sign as me", referring to the author's X post.
Many demonstrators lay on the floor as police arrested them, with around four to five officers carrying each protester to a van.
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British actor Alfred Enoch was among those in attendance at the demonstration and held a sign reading "this is democracy not terrorism".
He was not arrested by police.
Palestine Action's co-founder Huda Ammori is taking a legal battle against the government's decision to ban the group under anti-terrorism laws to the UK's highest court in a bid to quash the proscription.
(c) Sky News 2026: Dozens arrested outside court hearing Palestine Action ban challenge
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