“Is that mummy?” Few could fail to be moved by the excited voice of Gabriella Zaghari-Ratcliffe as she watched her mother, Nazanin, step back onto British soil for the first time since her arrest in Iran six years ago. Nazanin’s homecoming is a remarkable victory for her determined husband, Richard, and the millions of ordinary Britons who joined his long campaign for her release. More extraordinary still is Nazanin’s own survival through her traumatic detention, including four years locked up in Tehran’s notorious Evin Prison. Nazanin is known to have been tortured at the hands of the Iranian…