The image of King Arthwyr, the Bear Exalted, in medieval Welsh literature - be it in Welsh or in Latin - is the archetypal Celtic hero - a rough, vigorous, splendidly barbarian figure fighting boars and serpents, witches, dog-headed warriors and other dreaded enemies. He is often seen in conflict with the Church, and echoes the values and life-style of the Heroic society of the "Dark Ages." Forget the Romances of the Round Table, damsels in distress, tournaments and the glittering Christian emperor, which ocuurred centuries later.
Welsh history starts the Arthwyr timeline much earlier. He was born in Pen-Y-Chen (Head of the Oxen) today known as Boverton near Llantwit Major (once known as Tre Beferad). His life sees him through to The Sixth Century in which he dies in Britainy, where he is known as St Armel, The Iron Bear.
The Latin Historia Brittionum ("History of the Britons") - conventionally attributed to Nennius - was originally composed c. 829/30 A.D., and attached to it are a series of Mirabilia or "Wonders."
It states he was a great fighter, but he was no Arthwyr.