Thomas Cooper KC, Scotland’s lord advocate, wrote to the Home Office in June 1940, urging it to take action. “The dossier against Hahn is probably more extensive and more damaging than that against anyone,” he claimed. “MI5 know all about this man, who has been the subject of numerous reports for several years. He is either a dangerous spy or a British agent.” Cooper, who served as the Unionist MP for Edinburgh West, added: “Local feeling is getting beyond control. The district is seething with alarmist rumours.” He alleged that Hahn’s school was perfectly located and equipped as a centre...