When author J. K. Rowling described, in the third volume of the Harry Potter series, Harry Potter and the Prisoner of Azkaban, a most vicious and magical book, the Monster Book of Monsters, she was maybe thinking about magical books that, in years gone by, were deemed to contain such secrets that needed to be kept away from privy eyes, books for which methods were devised to keep them closed, locked away to the non-initiated.
While the idea of a “locked book” of secrets may seem something from a fairy tale, in the history of conjuring we have some books that have actually been published with a padlock and a key to keep them closed, in order that the casual observer could not learn the mystical secrets in the volume. These books were produced in the country of Harry Potter: England.