London’s Metropolitan Police said they detained 365 people on Saturday after demonstrators in Parliament Square openly backed the recently proscribed activist network Palestine Action. The crowd, estimated by police at about 500–600, unfurled placards stating “I oppose genocide. I support Palestine Action,” prompting officers to arrest anyone displaying the slogan. A further seven people were held for other offences, including five assaults on officers, though no serious injuries were reported. Parliament banned Palestine Action in early July under the Terrorism Act 2000, making membership of, or public support for, the group punishable by up to 14 years in prison. Home Secretary Yvette Cooper cited “serious attacks” by the organisation, including a 20 June break-in at RAF Brize Norton where activists sprayed red paint and used crowbars on two Voyager tanker aircraft, causing about £7 million in damage. Saturday’s rally was organised by campaign collective Defend Our Juries, which urged supporters to risk arrest to highlight what it calls an over-broad restriction on free expression. Deputy Assistant Commissioner Ade Adelekan had warned in advance that the scale of planned demonstrations across London would stretch police resources. The protest follows a High Court decision last week granting Palestine Action co-founder Huda Ammori permission to challenge the proscription on constitutional grounds. Civil-liberties groups, including Amnesty International, say the mass arrests underscore concerns that the expanded terrorism powers may criminalise non-violent dissent.