One day in November 1958, the celebrated historian Hugh Trevor-Roper received a curious letter. It was an appeal for help, written on behalf of a student at Magdalen College, with the unlikely claim that he was being persecuted by the Bishop of Oxford. Curiosity piqued, Trevor-Roper agreed to see the man calling himself ‘Robert Peters’. It was to be the start of an investigation he would pursue for the next quarter of a century.