Cadwaladr ap Cadwallon was a real person. His father, Cadwallon, was killed in the battle of Catscaul or “Cad-ys-gual”, the Battle of the Wall (Heavenfield, near Hexham) in 634 AD. An unknown usurper, Cadfael ap Cynfeddw, placed himself on the throne of Gwynedd, and was himself overthrown in 655 AD by the twenty-two year old Cadwaladr, Cadwallon’s son, who’d been raised in exile until he could return to claim his birthright.
Cadwaladr is mentioned in the following sources:
The Harlaein Genealogies: a collection of old Welsh genealogies preserved in British Library, Harleian MS 3859. They’ve been dated to the reign of Hwyel Dda (10th century). Cadwaladr is mentioned as the son of Cadwallon and the father of Idwal, all Kings of Gwynedd.
Annales Cambriae (the Annals of Wales): A single line: 682 – A great plague in Britain, in which Cadwaladr son of Cadwallon dies.
Historia Brittonum: This text was composed sometime between 828 and 830, attributed to Nennius. Of Cadwaladr ap Cadwallon, he states: “Catgualart (Cadwallader) was king among the Britons, succeeding his father, and he himself died amongst the rest. He slew Penda in the field of Gai, and now took place the slaughter of Gai Campi, and the kings of the Britons, who went out with Penda on the expedition as far as the city of Judeu, were slain.”
The Book of Taliesin: Taliesin was a Welsh poet born in the mid to late 6th century. Two poems are attributed to him that mention Cadwaladr. One is The Great Prophecy of Britain in which he rails against the Saxon incursions and praises the rule of Cadwaladr: “Cadwaladr is a spear at the side of his men; In the forest, in the field, in the vale, on the hill; Cadwaladr is a candle in the darkness walking with us; Gloriously he will come and the Welsh will rise . . .” (my interpretation)
The second is the Prediction of Cadwaladr, which is incomplete. It speaks of Cadwaladr, not Arthur, as the one who sleeps in the mountains to return at the nation’s greatest need.
History of the Kings of Britain: This is Geoffrey of Monmouth’s romantic and fanciful tale, telling the supposed story of the history of Britain from its founding by Brutus to the death of Cadwaladr.
The ‘Dark Ages’ were ‘dark’ only because we lack historical material about the period between 407 AD, when the Romans marched away from Britain, and 1066, when William of Normandy conquered England.
For Wales, the time was no more or less bright than any other. The relative peace the Romans brought was predicated on the brutal subjugation of the British people. When the Romans left, the Britons faced the Irish from the west, the Scots from the northwest, the Picts from the northeast and ‘Saxons’ (who were Angles and Jutes too, not just ‘Saxons’) from the east. To a certain degree, it was just more of the same. The Britons had their lands back—the whole expanse of what is now Wales and England—for about five minutes.
It does seem that a ruler named Vortigern invited some Germanic ‘Saxon’ tribes to settle in eastern England, in hopes of creating a buffer zone between the Britons and the relentless invasions from Europe. This plan backfired, however, and resulted in the pushing westward of successive waves of ‘Saxon’ groups. Ultimately, the Britons retreated into Wales, the only portion of land the Saxons were unable to conquer.
The rule of Cadwaladr ap Cadwallon sits at the resting point between the Welsh retreat and the Saxon advance. As romanticized by Geoffrey of Monmouth, he was the last Pendragon, the last King of Wales before the Cymry fell irretrievably under a wave of Saxon invaders.