The authors have discovered what happened to John Dee's most important manuscript, his book of personal angelic invocations which he kept in Latin, and how it was preserved and developed by 17th century magicians into a full working magical system. How only a small part of this material reached the Hermetic Order of the Golden Dawn in the 1880's. Even this was then suppressed by the chiefs of the Order, and it did not appear in Israel Regardie's monumental work on the Order rituals. They have also traced how the classical techniques of invocation and evocation drawn from late mediaeval grimoires, were passed through John Dee's magic, via Elias Ashmole, to the aristocratic angel magicians of the 17th century, including some of the most powerful and influential figures in England. In the 20th century many fanciful constructions were added to GD Enochian by writers such as Aleister Crowley, who were however all unaware of the completely developed system that already existed, and which is here published in full for the first time. Full transcription of 4 key magical manuscripts in the British Library, and in the Bodleian Library. The 17th century summation of John Dee's works.