Relations between Llywelyn and King John deteriorate in 1210.

J. E. Lloyd suggests that the rupture may have been due to Llywelyn forming an alliance with William de Braose, Fourth Lord of Bramber, who had fallen out with the king and had been deprived of his lands.

While John leads a campaign against de Braose and his allies in Ireland, an army led by Earl Ranulph of Chester and Peter des Roches, Bishop of Winchester, invades Gwynedd.

Llywelyn destroys his own castle at Deganwy and retreats west of the River Conwy.

The Earl of Chester rebuilds Deganwy, and Llywelyn retaliates by ravaging the earl's lands.

John sends troops to help restore Gwenwynwyn to the rule of southern Powys.