The prince of Gwynedd both fought and married into the English royal family.

Llywelyn seemed to be unable to avoid conflict with the Crown.

Llywelyn was able to capitalise, establishing himself as the foremost ruler of 'Pura Wallia' - the locally-run areas of Wales not under the control of the Marcher lords (Marchia Wallia). He was using the title 'Prince of the whole of North Wales' by 1200.

By 1200, he had attained control of Gwynedd, and at the same time, the kingdom of Deheubarth, which had been the most powerful of the Welsh kingdoms, was being divided among squabbling princes.

Llywelyn ab Iorwerth, the grandson of the famed Owain Gwynedd, was born at the old Dolwyddelan castle in about 1173.

His cousin, Gruffudd ap Cynan, ruler of Gwynedd west of the River Conwy died in 1200 and Llywelyn further expanded his territory. In 1201, his other cousin Maredudd ap Cynan, was arrested on a charge of treason and Llywelyn took his territories of Eifionydd and Llyn.

Llywelyn the politician raise his head in 1201 as he concluded a treaty with King John of England. In return for John's recognition of Llywelyn's territorial gains, he was to pledge fealty (allegiance) to the English monarch.

Emboldened by his gains and increasing power, Llywelyn moved against Gwenwynwyn ab Owain of Powys, his main rival in Wales. While the invasion was called off - thanks to the intervention of the clergy - Llywelyn had made his intentions clear. When he married Joan, the illegitimate daughter of King John, in 1205, he had married into the royal family.

He benefited from this cosy relationship when Gwenwynwyn was arrested and stripped of his lands by John. Llywelyn took the majority of his lands. He also fought alongside King John in a war against King William I of Scotland.

But things were not to remain rosy. He fell out with John, possibly due to an ill-advised alliance with a lord not in the king's favour. Gwynedd was invaded by Earl Ranulph of Chester, then in 1211 by King John and an alliance of almost all the other Welsh princes.

Military defeat was mitigated by his wife, who convinced her father not to strip Llywelyn of all his lands, and instead, he was restricted to lands west of the Conwy.

The fluid politics of the Welsh kingdoms resulted in an alliance forming between Llywelyn and the lords of Powys and Deheubarth against the now-unpopular King John.

Military success for the alliance followed, with territory regained during 1212 and 1213, with John under threat from assassination if he invaded in retaliation. John was at the time under attack from disillusioned lords who forced him to sign Magna Carta.

1215 saw Llywelyn truly earn his eptithet of The Great, with the castles of Carmarthen, Kidwelly, Llanstephan, Cardigan and Cilgerran falling to his alliance.

He was now leader of the free princes of Wales, and was ruler of the vast majority of the nation. In 1216 the other princes affirmed their allegiance to Llywelyn at Aberdyfi.

In 1218, John's successor Henry III, confirmed Llywelyn's possessions with the Treaty of Worcester. Intermittent disputes erupted over the next few years with the Marcher lords, but Llywelyn was always politically astute, using marriage to shore up his position - his daughters became wives of Marchers.

He embarked on a programme of castle building including Criccieth, Castell Y Bere, Dolwyddelan and Tomen Y Bala.

Llywelyn seemed to be unable to avoid conflict with the Crown, however, and mounted regular incursions across the border into English lands or picked fights with the likes of Hubert de Burgh, one of the most powerful men in England.

Largely, though, his position remained unchanged and he was able to exert a political power possibly never again reached by a Welsh prince. The Peace of Middle, agreed between Llywelyn and the king in 1234, was initially for two years, but was extended each year until Llywelyn died in 1240.