Cadwallon Lawhir, Caswallon, Catwallon
A North Welsh ruler who is, according to Geoffrey, said to have driven the Irish (led by Serigi) out of Anglesey about the year AD 500. After the noble victory in Mona (Anglesey), he built a church on the site, and called it Llan y Gwyddyl, later known as Cerryg y Gwyddyl, which is Welsh for 'Stones of Irishmen'. In later years he set up a royal court at Aberffraw, on the west coast of Anglesey.
The reason for his epithet is thought to be because of his long arms. Iolo Goch explains that he could
reach a stone from the ground to kill a raven, without bending his back, because his arms was as long as his side to the ground.
His family was a northern migrant and he was possibly the first generation to be born in Wales. His father was King Einion Yrth of Gwynedd, of whom he was the eldest son, and his grandfather was Cunedda Wledig. His son, Maelgwn Gwynedd, inherited the kingdom when Catwallaun died.
In Arthurian tradition he may be identical with Cadwallon who, according to Geoffrey, ruled Gwynedd in Arthur's time. Cadwallon was the father of Cadwallader and the King of the Vendotii, a people who lived in North Wales, principally Gwynedd.
Cadwallo Longhand | The Legend of King Arthur