This is about the historiographical convention. See History of Anglo-Saxon England for a historical discussion, and List of Anglo-Saxon kingdoms for a full list.The Heptarchy (from the Greek ἑπτά hepta, "seven" and ἄρχω arkho, "to rule") is a collective name applied to the Anglo-Saxon kingdoms of south, east, and central England during late antiquity and the early Middle Ages, conventionally identified as seven: East Anglia, Essex, Kent, Mercia, Northumbria, Sussex, and Wessex.