By his own admission J.R.R. Tolkien was captivated by a lifelong secret vice—but, before you raise the alarms, be assured: it’s not what you think. He was renowned as the avocational author of The Hobbit, The Lord of the Rings, andThe Silmarillion but his vocational calling was as a linguist and an Oxford don. He was a fellow of Pembroke College as a pr…