After Earl Harold had ravaged Gwynedd in 1063, this created a power vacuum that allowed Powys to extend its influence north over the next 100 years. The rulers of the ‘House of Mathrafal’ took their name from the castle and seat of power at Mathrafal, overlooking the Vyrnwy valley. Bleddyn ap Cynfyn became Prince in 1063 and allied himself with Edric the Wild, a Mercian land magnate, to attack Hereford castle in 1067. Then in 1068 he allied himself to Earl Edwin of Mercia and Earl Morcar of Northumbria in their rebellion against King William. He burnt the town of Shrewsbury, but was unable to take the castle.
William the Conqueror did not have a plan for the subjugation of Wales. He left this to powerful Lords that were installed in the border area – The Marcher Lords. They began this very effectively, and had subjugated the whole of Wales by 1090. However, they were unable to retain control, and by 1101 the boundaries of north Wales were back to where they had been.
The last strong Prince of Powys was Madog ap Maredudd, who ruled from 1132 to 1160. He extended the northern borders, taking control of Oswestry and Whittington castles in 1146. In 1150, he was defeated by Gwynedd and lost control of the Lal commute (Yale). But he recovered Lal by supporting Henry II’s campaign against Gwynedd in 1157.
By 1160 the northern section of Powys included English Maelor, and the geographical area around modern Holt, Wrexham, Llangollen and Corwen. The southern section included the modern towns of Welshpool, Newtown, Montgomery, up to the outskirts of Shrewsbury.