 Some historians believe that it was based on the old Carvetii tribal region – mostly covering the Solway plain and the Eden valley.Others say that it may have included large parts of Dumfriesshire, Lancashire and Yorkshire.The Kingdom's centre was based, possibly, at "Llwyfenydd", believed to be in the valley of the Lyvennet Beck, a tributary of the River Eden in east Cumbria, or, alternatively, at Carlisle.