practices, withdrew to Iona. Middle Anglo-Saxon history (660–899) By 660, 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. The development of kingdoms, with a particular king being recognised as an overlord, developed out of an early loose structure that, Higham believes, is linked back to the original feodus. The traditional name for this period is the Heptarchy, which has not been used by scholars since the early 20th century as it gives the impression of a single political structure and does not afford the "opportunity to treat the history of any one kingdom as a whole". Simon Keynes suggests that the 8th and 9th century was a period of economic and social flourishing which created stability both below the Thames and above the Humber. Mercian supremacy (626–821) Middle-lowland Britain was known as the place of the Mierce, the border or frontier folk, in Latin Mercia. Mercia was a diverse area of tribal groups, as shown by the Tribal Hidage; the peoples were a mixture of Brittonic speaking peoples and "Anglo-Saxon" pioneers and their early leaders had Brittonic names, such as Penda. Although Penda does not appear in Bede's list of great overlords, it would appear from what Bede says elsewhere that he was dominant over the southern kingdoms. At the time of the battle of the river Winwæd, thirty duces regii (royal generals) fought on his behalf. Although there are many gaps in the evidence, it is clear that the seventh-century Mercian kings were formidable rulers who were able to exercise a wide-ranging overlordship from their Midland base. Mercian military success was the basis of their power; it succeeded against not only 106 kings and kingdoms by winning set-piece battles, but by ruthlessly ravaging any area foolish enough to withhold tribute. There are a number of casual references scattered throughout the Bede's history to this aspect of Mercian military policy. Penda is found ravaging Northumbria as far north as Bamburgh and only a miraculous intervention from Aidan prevents the complete destruction of the settlement. In 676 Æthelred conducted a similar ravaging in Kent and caused such damage in the Rochester diocese that two successive bishops gave up their position because of lack of funds. In these accounts there is a rare glimpse of the realities of early Anglo-Saxon overlordship and how a widespread