[1] According to Nennius in the Historia Brittonum, Cadell was driven out of his father Cadeyrn Fendigaid's kingdom by Irish pirates during the chaos of the Saxon insurrection in Southern Britain.
He hid himself amongst the peasants of Powys and became a servant of the Irish chieftain, Benlli, hoping one day to find an opportunity to retrieve his inheritance.
His chance arose when the Roman clergyman Saint Germanus of Auxerre, visited Britain, probably for the second time in AD 447, to combat Pelagian views (opposition to Original Sin).
Travelling into the Midlands, Germanus heard of the pagan Irish stronghold and, with his many followers, laid siege to the Powysian capital.
It is unclear where the kingdom's capital was at the time; tradition suggests the Clwydian hillfort Foel Fenlli, the 'Hill of Benlli', while archaeological evidence points to Caer Guricon (Wroxeter, Shropshire).