Belief in magic was, until relatively recent times, widespread in Britain; yet the impact of such belief on determinative political events has frequently been overlooked. In his wide-ranging new book, Francis Young explores the role of occult traditions in the history of the island of Great Britain: Merlin's realm. He argues that while the great magus and artificer invented by Geoffrey of Monmouth was a powerful model for a succession of actual royal magical advisers (including Roger Bacon and John Dee), monarchs nevertheless often lived in fear of hostile sorcery while at other times they even attempted magic themselves. Successive governments were simultaneously fascinated by astrology and alchemy, yet also deeply wary of the possibility of treasonous spellcraft. Whether deployed in warfare, rebellion, or propaganda, occult traditions were of central importance to British history and, as the author reveals, these dark arts of magic and politics remain entangled to this day.