The political map of Lowland Britain had developed with smaller territories coalescing into kingdoms, and from this time larger kingdoms started dominating the smaller kingdoms. By 600, a new order was developing, of kingdoms and sub-Kingdoms. The medieval historian Henry of Huntingdon conceived the idea of the Heptarchy, which consisted of the seven principal Anglo-Saxon kingdoms. The four main kingdoms in Anglo-Saxon England were: East Anglia, Mercia, Northumbria (Bernicia and Deira), Wessex. The minor kingdoms were: Essex, Kent, Sussex