Ernest Moret, who works at Editions La Fabrique, was reportedly detained by police after arriving from Paris at St Pancras railway station on Monday evening. He had been due to attend a book fair in London.

A joint statement from his employers and London-based Verso Books read: “On arrival at St Pancras Station, Ernest was pulled aside by police officers acting under Schedule 7 of the Terrorism Act 2000 and detained for questioning without a lawyer present, allegedly to determine whether he was engaged in terrorist acts or in possession of material for use in terrorism.

“The police officers claimed that Ernest had participated in demonstrations in France as a justification for this act – a quite remarkably inappropriate statement for a British police officer to make and which seems to clearly indicate complicity between French and British authorities on this matter.

“It was demanded that he give up his phone and pass codes to the officers, with no justification or explanation offered. This morning, Ernest was formally arrested and transferred to a police station, accused of obstruction because of his refusal to give up his pass codes. He remains in police custody.

“We consider these actions to be outrageous and unjustifiable infringements of basic principles of the freedom of expression and an example of the abuse of anti-terrorism laws.”

Demonstrations are planned for Tuesday evening in front of the British Embassy in Paris and the French Embassy in London.

🚩 RDV à 20h devant l'ambassade de Grande-Bretagne pour exiger la libération d'Ernest !
📍 35 rue du Fbg St Honoré (Paris 8e) https://t.co/RpX4RgxnJH

— Action Antifasciste Paris-Banlieue (@AFA_Paris75) April 18, 2023

Protests against Emmanuel Macron’s pension reforms have been sweeping France for weeks, and there have been some acts of violence – including smashing windows, setting fire to bins and street furniture and scuffling with police – in cities including Paris.