Following Arthur’s reign, the fragmented petty realms proved ineffective in halting the advancing Germanic expansion or the raids by the Picts and Irish. However, determined local resistance enabled the Romano-Britons, also known as the Welsh, to maintain a presence in certain fortified positions derived from Roman towns or refurbished Celtic hillforts. The transition from Romano-British settlements to Welsh kingdoms during the 6th–8th centuries was undoubtedly marked by violence and confusion. Saxon victories at Deorham (577, likely located in south Gloucestershire) and Chester (604/616?) further fragmented the remaining pockets of resistance, cutting off land connections between regions such as modern Devon and Cornwall, Wales, and the northern kingdoms including Scotland.
Bryneichn
Bryneich, formed from the southern territories of the Votadini, possibly emerged as a result of the division of the militarized Roman ‘Old North’ (Yr Hen Ogledd) following Coel Hen’s death in 420. This kingdom may have been governed from Din Guardi (Bamburgh), eventually falling under Saxon control in 604.
Reghed and Cumbria
During the later years of Roman rule, the northern region was overseen by local rulers or Duces Britanniarum as proxies. The final figure in this line was Coel Hen, often associated with the legendary “Old King Cole” from nursery rhymes, who lived approximately between 350 and 420 AD. His realm encompassed the area from north of modern Liverpool up to Hadrian’s Wall, spanning coast to coast. After his reign, his kingdom was divided among his descendants into smaller entities.
Ebrauc and South Rheged
According to basic historical accounts, upon the passing of Coel Hen’s son, Mor ap Ceneu, northern Britain was split into Ebrauc to the east of the Pennines and Rheged to the west. In 535, Rheged was further divided into North Rheged and South Rheged. Rheged, later known as Cumbria, emerged as the most influential kingdom in the region under Urien (circa 530–590), a descendant of Coel Hen. Urien ruled from Carlisle, situated at the western terminus of Hadrian’s Wall, where Romanized governance and institutions persisted. While eastern territories increasingly fell under the control of the Anglo-Saxons from Bernicia, Rheged remained a stronghold of Romano-British resistance until its collapse in 730.
Elmet
Elmet (or Elfed) also surfaced during the late 5th-century fragmentation of Coel Hen’s realm. It occupied the land between the River Humber and Hadrian’s Wall, with some extensions north of the latter. Elmet appeared to be a continuation of the Roman military presence in the north. Its fall to the Saxons in 617 signaled the end of any realistic British prospects of maintaining control over the Pennines.
Manaw Gododdin
Archaeological evidence indicates that a local Romano-Christian aristocracy maintained authority over a region spanning modern northeast England and southeast Scotland until its demise in the mid-7th century. Within this territory, the tribal group known as the Votadini and their successors, the Manaw Gododdin, established a kingdom immortalized in the late 6th-century poem, Y Gododdin. This poem mourns the heroic warriors gathered by the lord of Din Eidyn (modern Edinburgh) to confront Saxon invaders from Deira at Catraeth (Catterick, Yorkshire). Despite sporadic connections to the Roman Empire, the poem reflects the sense of camaraderie among these warriors and their fellow Romano-Britons. Gododdin eventually succumbed to the Saxons of Bernicia around 640 AD.
Southwest and central-western Scotland were possibly inhabited by a group known as the Damnoni/Damnonii, though historical references to them are scarce, limited to a single 2nd-century source. The earliest mention of a potential kingdom in the mid-5th century, ruled by a king named Ceretic (also known as Coroticus or Guletic), comes from a letter attributed to St. Patrick. By the late 6th century, this dynasty likely held sway over a territory extending at least from the Firth of Clyde southwestward into Cumbria. Its rulers held the title of reges of Alo Cluathe/Alt Clut (‘Kings of the Clyde Rock’), with a formidable stronghold at Dùn Breatann (‘Fort of the Britons’). Annexed by the Northumbrian Saxons at the start of the 7th century, Strathclyde regained its independence in 685 after the Battle of Nechtanesmere. However, in around 750, an alliance between the Northumbrians and Picts posed a threat to Strathclyde. Consequently, the Northumbrians seized much of the western territory from the Britons, ultimately forcing their submission in 756.
Gwynned, Dyfed and Powys
Fortified settlements dating from the 5th to 7th centuries are interpreted as centers of power associated with an emerging post-Roman elite. Notable among these are Dinas Emrys in northwest Wales and Bwrdd Arthur on Anglesey, often referred to as ‘Ambrosius’s Town’ and ‘Arthur’s Table,’ respectively. By the late 6th century, the tribal territory of the ancient Ordovices in north Wales gave rise to Gwynedd, likely the most militarily potent of the kingdoms in Britannia Prima. Gildas also mentions Vortiporius, known as the ‘tyrant of the Demetae,’ ruling over the civitas that would evolve into the kingdom of Dyfed in southwest Wales, where a Romano-British elite persisted well into the 11th century.
According to Kenneth Dark, the civitas of the ancient Silures fragmented in the 6th century into Gwent in eastern Wales (derived from the Roman Caerwent – Venta Silurum) and Glywysing (Glamorgan) to the west, governed by chieftains dwelling in hillforts. The Llandaff Charters indicate the existence of major and minor kingdoms during the 5th–8th centuries, including Ceredigion, Builth, and Gower. Consolidation occurred in the 7th–8th centuries, with the seats of the high kings of Wales located in Glamorgan in the northwest, Deheubarth in the south, and Powys in eastern central Wales. Smaller entities were absorbed, and their kings reduced in status to leading men or uchelwyr.
Dinas Powys emerged as a crucial center in Wales during the 5th–7th centuries, serving as the court of a chieftain within a Romano-Celtic aristocracy. This chieftain attracted warriors around him, mirroring Imperial governance. Poetic works attributed to Taliesin praise Selyf’s father Cynan, suggesting that the king of Powys launched aggressive and successful campaigns against other Welsh leaders, including a notable expedition across Gwynedd into Anglesey. Over the following centuries, Powys would forge a formidable alliance with neighboring Mercia against Saxon Northumbria.
Dumnonia
The civitas of the Dumnonii, inhabitants of Cornwall and Devon, eventually evolved into the kingdom of Dyfneint. In the late 5th century, Dumnonia appeared as one of the most prosperous regions of Britain, likely capable of fielding a reasonably robust military force. With its extensive coastlines and maritime heritage, it was strategically positioned for transporting troops both across the English Channel and around Brittany. According to Gildas, Dumnonia was governed by the ‘tyrant’ Constantine (Custennin), the son of Cynfawr and Duke Cador of Cornwall.
Archaeological findings suggest the minting of potential royal coins or tokens in pewter bearing the likeness of a rex, possibly depicting Elabius, who met Germanus of Auxerre in 429. Kenneth Dark proposes that the elites of 5th–6th century Dumnonia, possibly descending from the Romano-British civitas, governed sub-kingdoms centered around hillforts, all pledging allegiance to the ruler of Dumnonia headquartered at Tintagel.
Other Romano-British enclaves
At Lowbury Hill, situated just off the Ridgeway at Aston Upthorpe in Berkshire, archaeologists have uncovered a rich warrior burial dating back to around 650–700. This burial site is located near an ancient Roman temple overlooking Wallingford, known as ‘Welsh people’s ford’, which interestingly was originally a native settlement rather than a Saxon one. The spearhead found at the site features a unique enamel decoration believed to be of Celtic origin. Isotope analysis of the warrior’s teeth strongly suggests that he was a Celtic Briton who grew up in western Cornwall. This discovery indicates that post-Roman Britons maintained a significant presence in the Berkshire area for a longer period than previously assumed.
Additionally, Kenneth Dark has used cemetery site patterns to argue that, at least during the 6th century, eastern Britain was not a uniform Anglo-Saxon region but rather a mosaic of diverse communities. Some communities were entirely British or of mixed origins, and Romano-British enclaves, such as Deira in the north, persisted for a considerable time despite the prevailing Anglo-Saxon influence.