Gwenddolau was king of a Briton realm situated about Liddel Water on the modern English-Scottish border near Luguvalium (Carlisle) just beyond Hadrian’s Wall. Gwenddolau claimed descent from Coel Hen (Coelestius Senex), the last Roman Dux Britanniarum, but could have been of the line of Antonius Donatus, appointed in the late 4th century to bring order to the region of the Selgovae of modern Dumfries and Galloway.
   King Gwenddolau fought and died in battle around 573CE. The battle was fought about eight miles north of Carlisle at Arderydd (Arfderydd, Armterid), now called Arthuret. The battle is remembered in the Welsh Triads as one of the “Three Futile Battles of the Isle of Britain,” so called because it was fought over “a lark’s nest” which may be a pun referring to the nearby fortress of Caerlaverock, whose name means “fort of the lark.” Different scholars speculate on his opponents, ranging from Riderech, ruler of the Clyde, Peredur who ruled the Pennines and Eboracum (York), and a few Urien of Rheged. The Scottish Merlin, Myrddin ab Morvryn, went mad after the battle when his lord was killed and in some of the poetry attributed to him seems to indicate fear of Riderech and his men. My own speculations tend toward Peredur who was trying to consolidate power in the region. Peredur and his cousin Gwrgi perished in battle around 580CE. Following his death, Riderech expanded his domains from the Clyde to include the region of Dumfries and Galloway creating the larger kingdom of Strathclyde. It is also at this time that Urien seems to rise to the role of command of the forces allied against the Angles. Rheged was based upon Carlisle and probably consisted more or less of modern Cumbria.