Photo by Entertainment One Medieval forms persist. Pilgrimage, Jonathan Sumption’s first book, published in 1975 when he was still an academic before he turned lawyer and controversialist, is a wonderfully detailed study of the entire phenomenon, as practised from late antiquity to the Reformation, relishing all its peculiarities. Pilgrimage, he concludes, maintains a fitful existence to this day. The needs it serves are perpetual perhaps. The Unlikely Pilgrimage of Harold Fry, published in 2012, was the debut novel of radio dramatist Rachel Joyce, developed from a short radio play to become one of the best-sellers of the year. She has…