By means of the Treaty of Montgomery (1267), Llywelyn ap Gruffydd was able to get his new title 'Prince of Wales' acknowledged by the English king Henry III.

Llywelyn ap Gruffydd finished the work his grandfather, Llywelyn the Great, had started: by force and diplomacy all the other Welsh dynasties were brought under his authority. Both Llywelyns were princes of Gwynedd and thus succeeded in expanding their territories. These territorial gains and Llywelyn ap Gruffyd's title 'Prince of Wales' were finally acknowledged by Henry III in 1267.