In Wales, the Cyfraith Hywel was codified by Hywel Dda c. 942 – 950.

A meeting at Eamont Bridge on 927 was sealed by an agreement that Constantine, Owen of Strathclyde, Hywel Dda, and Ealdred would " renounce all idolatry ": that is, they would not ally with the Viking kings.

He was accompanied by many leaders, including the Welsh kings Hywel Dda, Idwal Foel, and Morgan ab Owain.

The following year, Constantine was again in England at Æthelstan's court, this time at Cirencester where he appears as a witness, appearing as the first of several subject kings, followed by Owen of Strathclyde and Hywel Dda, who subscribed to the diploma.

There would be two national universities ( one in the south and one in the north ) and return to the traditional law of Hywel Dda.

Davies suggests that the texts of Welsh law, traditionally codified by Hywel Dda at Whitland, were first assembled in book form under the aegis of Rhys.

* Hywel Dda (" the Good ") of Wales

Rhodri's grandson, Hywel Dda ( Hywel the Good ), formed the kingdom of Deheubarth by joining smaller kingdoms in the southwest and had extended his rule to most of Wales by 942.

* The Welsh ruler Hywel Dda (" Hywel the Good ") merges Dyfed and Seisyllwg, establishing a new kingdom known as Deheubarth.

* Hywel Dda, king of Deheubarth, annexes Gwynedd and Powys to become ruler of most of Wales.

He was accompanied by many leaders, including the Welsh kings Hywel Dda, Idwal Foel, and Morgan ab Owain.

The following year, Constantine was again in England at Æthelstan's court, this time at Cirencester where he appears as a witness, appearing as the first of several subject kings, followed by Owain of Strathclyde and Hywel Dda, who subscribed to the diploma.

Yet it is also possible that some Welsh kings, in particular Hywel Dda, were benefiting from this relationship.

* Kirby, D. P., ' Hywel Dda: Anglophil?

The ( Welsh ) Laws of Hywel Dda, originally compiled around 900 A. D, identify a bard as a member of a King's household.

One of many collections of Welsh genealogies, this documents the lineage of Hywel Dda, king of Wales, and several of his contemporaries.

Wotton began to study Welsh, and produced an important bilingual parallel text edition of the Welsh and Latin texts of the medieval Welsh laws traditionally attributed to Hywel Dda at the request of his friend.

* Cyfreithjeu Hywel Dda ac eraill, seu Leges Wallicae Ecclesiasticae et Civiles Hoeli boni et Aliorum Walliae Principum ( London, 1730 )

Wales then developed its own system of law, first codified by Hywel Dda ( Hywel the Good ; reigned 942 – 950 ) when he was king of most of Wales.

Deheubarth was founded circa 920 by Hywel Dda (" Hywel the Good ") out of the territories of Seisyllwg and Dyfed, both of which had come into his possession.

* Hywel ap Rhys ( died 1231 ) spent many years as a hostage at the court of Henry II and on his return became known as Hywel Sais ( Hywel the Saxon, i. e. Englishman ).

* Maredudd ap Rhys ( died 1239 ) was also given as a hostage, but was less fortunate than Hywel.

* Aeddan ap Blegywryd, prince of Gwynedd succeeds Cynan ap Hywel.

In 1143 Cadwaladr was implicated in the murder of Anarawd ap Gruffydd of Deheubarth, and Owain responded by sending his son Hywel ab Owain Gwynedd to strip him of his lands in the north of Ceredigion.

* Rhodri ap Hywel, king of Deheubarth

Family names in many Celtic, English, Iberian, Scandinavian, Armenian and Slavic surnames originate from patronyms, e. g. Wilson ( son of William ), Powell ( from " ap Hywel "), Fernández ( son of Fernando ), Rodríguez ( son of Rodrigo ), Carlsson ( son of Carl ), Petrov ( of Peter ), Stefanović ( son of Stefan, little Stefan ) and O ' Connor ( from " Ó Conchobhair ", meaning grandson / descendant of Conchobhar ).

His father was supposed to be Siôn ap Dafydd ap Madog ap Hywel Moetheu of Porth-y-ffin, also near Tregaron.

Several kings, including Hywel ap Rhys of Glywysing and Hyfaidd of Dyfed ( where Asser's monastery was ), had submitted to Alfred's overlordship in 885.

From 1243 de Clare was actively extending his authority in Glamorgan ; in 1245 he seized the manors of Llanblethian and Talyfan from Richard Siward, and the lordships of Miskin and Glynrhondda from Hywel ap Maredudd.

The first-known poem in English by a Welshman was Hymn to the Virgin written c. 1470 by Ieuan ap Hywel Swrdwal.

While historically Welsh writing in English might be said to begin with the fifteenth-century bard Ieuan ap Hywel Swrdwal, well into the nineteenth century English was spoken by few in Wales, and prior to the early twentieth century there are only three major Welsh-born writers who wrote in the English language: George Herbert ( 1593 – 1633 ) from Montgomeryshire, Henry Vaughan from Brecknockshire ( 1622 – 1695 ), and John Dyer from Carmarthenshire ( 1699 – 1757 ).

A civil war in Gwynedd in the 810s ended with the succession of Hywel ap Caradog in 816 or 817, and Coenwulf invaded again, this time ravaging Snowdonia and taking control of Rhufuniog, a small Welsh territory near Rhos.

* Rhys ap Hywel: Jason Francis

The sound of the crwth was described by medieval poet Gruffydd ap Dafydd ap Hywel as ' in the hand a hundred voices ' ( yn y llaw yn gan llais '), referring to the rich sound of six strings sounded simultaneously in harmony.

In the 14th century the castle had a notable later constable called Hywel ap Gryffd who fought for Edward III at the Battle of Crecy in 1346.

* A is written in a hand of about 1100x1130 AD, and inserted without title into an MS. of the Historia Brittonum where it is immediately followed by a pedigree for Owain ap Hywel ( d. 988 ).

* Rhodri ap Hywel 950-953

* Edwin ap Hywel 950-954

He built a castle in the commote of Mabudryd, but Cadell, aided by Hywel ab Owain Gwynedd who held Ceredigion for Gwynedd, destroyed it in 1146.

He was a grandson of Cadell ab Einion ab Owain ab Hywel Dda, and a great-grandson of Einon ab Owain ap Hywel Dda thus great-great grandson of Hywell Dda ( Howell the good ), king of the Britons ; who fell in 984.

By normal custom Idwal's crown should have passed to his sons, Ieuaf and Iago ab Idwal, but Hywel Dda intervened and sent Iago and Ieuaf into exile in Ireland and established himself as ruler over Gwynedd until his death in 950 when the House of Aberffraw was restored.

The principality retained a great degree of autonomy, characterized by a separate legal jurisprudence based on the well established laws of Cyfraith Hywel, and by the increasingly sophisticated court of the House of Aberffraw.