Llywelyn-Ap-Gruffyd rose to power in Snowdonia (Gwynedd)  in 1255 after the death of his uncle Daffyd-Ap-Llywelyn in 1246. Gwynedd was then the heartland of welsh resistance to the English. Llywelyn took advantage of this and the resentment to English officers that had been aroused in the lands to the east of the river Conwy, by tactlessly ignoring local custom, to extend his power into the wider Gwynedd of his forbears. "The Welsh proud of their descent from the Trojans, had risen in defence of their patrimony and achieved a unity such has had never been Known before."

    Llywelyn was recognized as Prince of Wales by Henry III and his son Edward at the treaty of Montgomery in 1267. His time as prince would not be a simple affair. At odds not only with some of the Marcher lords, such as Roger De Mortimer an implacable enemy, he was also at risk from within his own dominions. Needing money to further his political aims he resorted to harsh methods that resulted in friction with his barons, to the extent that even his brother Daffyd conspired to have him killed.

    Edward returned from the eighth crusade in the Holy lands in 1274 to almost open hostility between Llywelyn and his administrators over land rights and castle building. It was not until 1277 that Llewellyn was forced to surrender to the might of Edwards’s army having been deserted by his vassals. An agreement negotiated at Aberconwy allowed Llywelyn to retain Snowdonia for his lifetime, despite Edwards apparent will to disinherit him completely. This was however on the condition that Llywelyn recognizes the hereditary rights of his brother Daffyd to a share of Snowdonia.

   The war of 1282 was instigated by Daffyd rather than  Llywelyn, who despite his grievances preferred more political solutions, perhaps influenced by his wife Eleanor de Montfort. Llywelyn did not join his brother until June that year, after his wife died giving birth to their daughter. His participation in the welsh rebellion gave it great strength; and it was not until late Autumn before Edward was in a position to attack Snowdonia. Llywelyn hoping to revive Welsh resistance in the lands to the south moved to Builth where he died in combat on December 11th 1282.

   His severed head was taken to the king in Rhuddlan and then displayed at the Tower of London. The Welsh poet Gruffyd ab yr Ynad Coch composed a magnificent elegy in which he described Llywelyn’s death as " A disaster of cosmic proportions " Daffyd was captured soon after in 1283 at his stronghold in Snowdonia, convicted of Treason, he was hanged, drawn and his quarters sent to four English cities. Llywelyn’s lands were united and annexed to the crown of England, and brought directly under English royal administration. Now Edwards attentions turned to the Scots.