In his own age, John Dee’s was a name to conjure with, as it is in ours. To say that he led a remarkable existence is an understatement of some order. Born six years before his most consistent (and consistently unreliable) patron, Elizabeth I, he also outlived her by six years. Over the course of his long life he established a reputation as Renaissance England’s most famous ‘magus’, and he was received not only at the royal court of Elizabeth but at that of the mercurial Habsburg emperor, Rudolph II. In his own mind, Dee was a master of occult (hidden) knowledge, an inspired visionary, with schemes for unlocking the secrets of nature and reunifying a divided Christendom. To his critics (and there were many), he was a disreputable conjuror, if not a dealer with evil spirits.

The life and works of Dee might seem like a gift to the biographer, but they also pose considerable challenges, even beyond those of tracking his movements across Europe to Cracow, Prague and other places. Dee’s astrological, alchemical and cabbalistic interests are extraordinarily complex and technical (‘the particle physics of