This book presents the results of an examination into the origins of King Arthur and the historical events associated with him and include discussions on the problems with dating in the Dark Ages and the influences of external environmental and astronomical events. The book also investigates the Celtic origins of the Grail stories and the significance of their appearance at the time of the crusades after the second fall of Jerusalem in 1187 and their re-emergence in Malory's Mort D'Arthur following the destruction of Constantinople in 1454.