chapter 2._

"After the territorial boundaries had become more settled, there appeared at the commencement of the seventh century seven or eight greater and smaller kingdoms. ... Historians have described this condition of things as the Heptarchy, disregarding the early disappearance of Sussex, and the existence of still smaller kingdoms. But this grouping was neither based upon equality, nor destined to last for any length of time. It was the common interest of these smaller states to withstand the sudden and often dangerous invasions of their western and northern neighbours; and, accordingly, whichever king was capable of successfully combating the common foe, acquired for the time a certain superior rank, which some historians denote by the title of Bretwalda. By this name can only be understood an actual and recognized temporary superiority; first ascribed to Ælla of Sussex, and later passing to Northumbria, until Wessex finally attains a real and lasting supremacy. It was geographical position which determined these relations of superiority. The small kingdoms in the west were shielded by the greater ones of Northumberland, Mercia and Wessex, as though by crescent-shaped forelands--which in their struggles with the Welsh kingdoms, with Strathclyde and Cumbria, with Picts and Scots, were continually in a state of martial activity. And so the smaller western kingdoms followed the three warlike ones; and round these Anglo-Saxon history revolved for two whole centuries, until in Wessex we find a combination of most of the conditions which are necessary to the existence of a great State."

_R. Gneist, History of the English Constitution,