The extraordinary initiation of the famous Successor to Alexander the Great, Demetrius Poliorcetes ('The Besieger of Cities') into the Eleusinian Mysteries in the late fourth century was viewed as an act of sacrilege by the biographer Plutarch 400 years later, and has passed into a canonical catalogue of iniquities perpetrated by his subject from 304-302 BC. Scholars have predictably followed the Pied Piper from Chaeronia, and added this incident to Demetrius’ juicy sexual antics with his favourite whores in the opisthodomus of the Parthenon, and many other (to the prude) lamentable peccadilloes. The more shocking sin, however, is a historiographic one: BOTH literary sources have misplaced the irregular Eleusinian initiation, and have derailed scholarship for two millenia! The occurrence of a single word in an Athenian inscription honouring one of Demetrius’ officers, a certain Medon, corrects the chronography, and has profound repercussions for the historical narrative and modern scholarly interpretations.