"The general pattern of political development during the eighth and ninth centuries could be reduced to a struggle for supremacy in which success was dependent on the ability of one king or another to harness the resources at his disposal in pursuit of a preconceived political end. Such a view would depend, however, on the tacit espousal of certain concepts which have long been central to the study of Anglo-Saxon history, but which may distort the perceptions of political power current in the period itself. One is the concept of the Anglo-Saxon 'Heptarchy', which proceeds from an observed distinction between the three 'Anglian' kingdoms of Northumbria, Mercia and East Anglia, the three 'Saxon' kingdoms of Wessex, Sussex and Essex, and the 'Jutish' kingdom of Kent, and which appears to provide the framework within which political development took place. It invites the supposition that each of the kingdoms should be understood in similar terms, and it creates the impression that the kingdoms were the constituent parts of an identifiable whole; yet the concept of 'Heptarchy' is, of course, no more than a sixteenth-century refinement of a twelfth-century rationalisation of Bede's incidental remarks on the political complextion of England in his own day. A second pervasive concept is that of the 'Bretwalda', or overlord of the southern English kingdoms. It springs from Bede's famous list of seven kings who ruled 'all the southern kingdoms' (HE II.5), as extended by a late ninth-century chronicler who added an extra name to the list, stating that he was the 'eighth king who was Bretwalda.' The implication is that there was a particular form of overlordship designated by a specific title (which would appear to mean 'ruler of Britain'), and that it was the struggle for this distinction which provided the organising principle of interaction between kings in the eighth and ninth centuries. The concepts of the 'Heptarchy' and 'Bretwalda' are so deeply engrained in the historiography of early Anglo-Saxon England that they could never be removed from any discussion of the subject; but it is questionable whether either concept would have had much meaning in the eighth or the ninth century, and it must be said that there are other ways of approaching the complexities of political history in this period, which proceed from different assumptions and which promise to explain developments in somewhat different terms."
Simon Keynes, 'England, 700-900' in New Cambridge Medieval History II, c.700-c.900. ed. Rosamond McKitterick, (Cambridge: University Press, 1995), p.19