Mohammed Elshimi, a researcher at the Royal United Service Institute, a think-tank, said this was the hardest task of all. “It’s a lot simpler for the home secretary to remove Shamima Begum’s passport . . . than to deal with the challenges of her repatriation and reintegration. Mr Elshimi believes the key problem is that even after a series of interventions, it is difficult to establish accurately whether the risk posed by former extremists has declined. “Even if you treat someone nicely, we know that from previous experience someone who successfully disengages can re-engage again 10 years later,” he said.