 The 7th century saw the rise to power of the Anglo-Saxon Kingdom of Northumbria (just as the 8th saw the rise of Mercia, and the 9th that of Wessex).The Northumbrian kingdom was based on the expansionist power of Bernicia, which, by 604, had taken over their neighbouring kingdom of Deira, along with other kingdoms of the Old North such as Rheged, although the dating of the takeover, and the extent of the Anglo-Saxon settlement that followed, are a matter of contention amongst historians.Documentary and archaeological evidence is lacking and qualified reliance is placed on place-names, sculpture and blood-group studies, all of which are open to challenge.