In the conditions of Wales, geographically divided by mountains and valleys, much depended on the prowess and sagacity of individual rulers, and kingdoms could expand and contract at speed. gwent took its name from Caerwent, the Roman base, and lay between the rivers Usk and Wye. By the ninth century it had been taken over by Morgannwg, and after 1066 most of it fell quickly to the Norman advance. To the west was glywysing, ruled over c.600 by Meurig ap Tewdig. It became part of morgannwg which, after the Conquest, formed the lordship of Glamorgan. West again was the kingdom of dyfed. Ruled by Llywarch ap Hyfaidd until 904, it became part of seisyllwg when his daughter married Hywel Dda, and was eventually incorporated into Deheubarth. Norman penetration into Pembroke-shire was rapid. North of Gwent lay brycheiniog, up the Usk valley to Brecon, and reputedly founded by Brychan, son of an Irish chieftain of the fifth century. Brychan was reported to have had twenty-four daughters and to have led his men to a devastating victory over their neighbours from Deheubarth. But in the tenth century it fell to Deheubarth and soon after the Conquest became part of the Norman lordship of Brecknock. North of Brycheiniog was builth, which dwindled from a small kingdom into a cantref. Nennius, in the Historia Brittonum, compiled in the early ninth century, named Ffernfeal as the ruler, adding that he also reigned in Gwerthrynion to the north-east, and tracing his ancestry back to Vortigern. It was absorbed into Gwynedd and, after the Conquest, much of it became the lordship of Radnor. To the west was ceredigion, a coastal kingdom between the rivers Teifi and Dovey. It was said to be the region to which Cunedda moved after his migration from southern Scotland, and to have been ruled by his son, Ceredig. Seisyll, king in the eighth century, gained territory to the south, but the expanded kingdom of Seisyllwg became part of Deheubarth.
Another small kingdom with strong links to south Wales was dumnonia (Cornwall), which included for a time Devon and part of Somerset. In the early eighth century its king, Geraint, received a letter from Aldhelm, bishop of Sherborne, advising him on the correct date of Easter. The region was incorporated into Wessex in the early ninth century by Ecgberht, and rebellions in 825 and 838 failed to restore its independence.
Subjects: British History.