The Library of St John the Beheaded was a secret library of forbidden texts, owned by the Catholic Church and located in London. The Doctor had been a patron of the library since his first incarnation, when he had visited there with Susan. (PROSE: All-Consuming Fire) It was part of the Vatican's accumulation of items they deemed unwise for the general public to know about, along with the Collection of Necessary Secrets and the Crow Gallery. (PROSE: Christmas on a Rational Planet)