I don't have John Morris' book, but the questions posted about it caught my interest. My thoughts had always been that with the Roman collapse, York as capital of the northen area, and a major roman civitas, probably held on with some semblance of Romano-British administrative structure until it became part of Saxon Bernecia (Brynaich). They weren't very accustomed to defending themselves. Ida and his folk founded Bamburgh about 50 years before the date mentioned by Brian for the fall of Peredur's kingdom (597), and this was just a few years before the final melding of Bernecia and Deira into Northhumberland by Aethelfrith and Edwin. Elmet was a small British kingdom in the Leeds area that was annexed about the time Rheged was conquered, but this is much later than you mention and I can't find any reference to their capital being York. In any case, Peredur has always seemed a name associated with post-Norman embellishments of older tales, and I have never seen it in any regal-lists. This is not to say that there were not a number of smaller British kingdoms in the time you mention that left no trace, perhaps because it was not important to the aristocracy in Wales to trace their lineage back to them as was the case with the Votadini/ Gw+yr Gogledd and the princes of Gwynedd. I would very much like the reference Mr. Morris used for his statement, and hope somebody else can suggest a name for 'Peredur's Kingdom'. To address your other question about the fate of Rheged: My own philosophy of history and pseudo-history is that often gradual take-overs of territory were later turned into one cataclysmic battle through bardic poetic license, representing the loss as felt by later generations. Canu Heledd probably represents such a case, with the later (9th C.?) poet mourning the incremental but relentless Mercian takeover of Powys. I nonetheless do believe that Cyndyylan was a 'real' Prince of Powys, although the poems themselves may not represent his true end. Rheged probably became subject to Edwin's control after Urien's death, both through war and diplomacy-- he may have married one of Urien's daughters. Strathclyde probably expanded a bit at Rheged's expense also. Certainly by the time Cadwallon invaded and ravaged Northumbria, the area was under Saxon control. Kim