Ms Begum is a British woman currently detained in Syria. She is one of three schoolgirls who travelled to Syria to join Islamic State in February 2015, at the age of 15.

The court unanimously allowed Ms Begum’s appeal, ruling that she must be readmitted to the UK in order to fully and effectively appeal against the deprivation of her citizenship.

The court found the Home Secretary’s “suggestion that Ms Begum’s appeal should be stayed indefinitely in circumstances where she is being detained by the SDF in the camp, does nothing to address the foreseeable risk if she is transferred to Iraq or Bangladesh, which is that in either of those countries she could be unlawfully killed or suffer mistreatment”.

It added that any risk Ms Begum might pose “could be addressed and managed if she returns to the United Kingdom”, noting that “If the Security Service and the Director of Public Prosecutions consider that the evidence and public interest tests for a prosecution for terrorist offences are met, she could be arrested and charged upon her arrival in the United Kingdom and remanded in custody pending trial. If that were not feasible, she could be made the subject of a TPIM.”

Reprieve is advocating for all Britons currently held in camps in North East Syria (NES) to be repatriated to the UK.

A very small fraction of the detainees currently held in NES are British. Of these, the majority are children. Reprieve estimates that there are between 15 and 20 family units in total.

There have previously been suggestions that Britons could be sent to Iraq, where they would likely face the death penalty with no prospect of a fair trial.

Human Rights Watch has reported that trials of suspected IS members “are summary and often do not put forward evidence of specific offences”, while “interrogators routinely use torture to extract confessions, and in most cases judges ignore torture allegations from defendants”.

The UK government itself has previously acknowledged the widespread use of torture and the death penalty across the Iraqi criminal justice system.

Maya Foa, Reprieve director, said: “It was always unsafe and unjust to make Brits in Syria someone else’s problem, and today it has been ruled unlawful. The government must urgently revisit its policy and repatriate the tiny number of remaining British families, to face British justice wherever there are charges to answer.”