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Celtic Kingdoms of the British Isles

Celts of Britain


Dumnonia / Defnas (Romano-Britons)
Incorporating Caer Penhuelgoit, Caer Rydh, & Caer Uisc

FeatureWith the expulsion of Roman officials in AD 409 (see feature link), Britain again became independent of Rome and was not re-occupied. The fragmentation which had begun to emerge towards the end of the fourth century now appears to have accelerated, with minor princes, newly declared kings, and Roman-style magistrates all vying for power and influence while also facing the threat of extinction at the hands of the various barbarian tribes which were encroaching from all sides.

FeatureBritain's south-west was dominated by a large and well-founded Celtic kingdom which took in all of Cornwall (Cornubia), Devon (Dyfneint), and much of Somerset (the 'Summer Land' of the Mabinogion - see feature link). Formed as the kingdom of Dumnonia by the long-dominant Dumnonii tribe here, it apparently emerged much earlier than many of its peers, perhaps up to two hundred years earlier than equivalents in the rest of modern England, while in Wales the picture is more confused.

FeatureHowever, much of this claim to early independent or semi-independent kingship may only have been established much later in the kingdom's history, perhaps based on an oral tradition which expanded the standing of a line of prominent native administrators. To put it simply, Dumnonia may not have been a kingdom in any real sense until the late fourth or early fifth century (see feature link).

One of the curiosities of late Roman Britain is the appearance of stones which recorded building or repair work on Hadrian's Wall. The stones are undated but are placed in the mid-fourth century, and two of them record work by the civitas Dumnoniorum and the civitas Durotrigum. They seem to represent either an enforced labour party under military supervision (which would not discount the possible presence of a semi-independent Dumnonia), or the provision of civilian labour to maintain the country's defences (which would still not mitigate against semi-independence).

Dumnonia's original capital would have been Isca (translated as the 'city of water', late British Caer Uisc, modern Exeter). There are several words for 'water' in common Celtic. The one required here is *iskā, from which Isca was taken and which is still in use today in a slightly modified form as 'exe' (for the River Exe, plus Exeter, Exton, and Exmouth, all of which follow the Exe out to sea).

The Cornish word for the River Exe is Eesk. It is interesting to note that various dialects of Celtic language use a different word, and this one seems to have fallen out of use everywhere else. Welsh uses 'dwr', and Cornish uses 'dowr', although the River Usk in South Wales is another Isca in modern form. In Cornwall 'Eesk' only survives as a remnant of former Dumnonian unity in the south-west.

Isca has also been known as Caer Rydh, the 'red city', from the colour of the red Devonshire soil around it, and Caer Penhuelgoit by Geoffrey of Monmouth - the 'prosperous chief city in the wood'. This is backed up by the writer of an old, local, legal document who called it Pennehaltecaire, meaning 'the chief town upon the hill'. Both usages may have been later, possibly a reaction to West Saxon occupation, with the Britons wanting to have their own, Brythonic name for their city.

FeatureAlthough under nominal Roman control even in the late fourth century (despite the possibilities mentioned above for some form of de facto independence), the Dumnonii probably exercised a certain amount of self-government in their own lands. The Romans clearly found the Dumnonians to be fierce in their resistance to invasion, and it is thought that the two sides reached an understanding whereby the Dumnonians would be cooperative clients if the Romans left them alone. They most probably re-established their kingdom as a power in its own right by the time of Magnus Maximus (see feature link), as the latter prepared Britain's defences prior to establishing his own claim for control of the Roman empire in AD 383. Dumnonia is perceived to have been fully independent by 410.

FeatureArchaeology confirms that the site of Roman Isca was abandoned in the fifth century. This is too early for it to have been due to West Seaxe pressure, although piratical raids along the coast could have contributed. Abandonment may have been part of the general preference for countryside living as cities began to fail due resources and sources of supply dwindling or being cut off entirely. Even so, given the later advances of the West Seaxe, the capital - wherever it was - would have been relocated to new locations to the west, time and time again.

Also by the fifth century, the kingdom seems to have incorporated the former territory of the Durotriges. The most likely reason for the failure of the Durotriges to reform as a post-Roman state is the slaughter of their nobility by the Romans during their fanatical resistance to invasion in AD 43. Now Dumnonia dominated the whole of the south-west, although that does not rule out either Caer Durnac (Roman Durnovaria, modern Dorchester in Dorset) or Wareham (the site of several early British memorial stones) perhaps hosting a regional power base or sub-kingdom.

With the apparent abandonment of Isca (Exeter) as a capital in the fifth century, what replaced it? In 2016, the Cornwall Archaeology Unit undertook the beginnings of a fresh dig at Tintagel in Cornwall. They uncovered thick foundation walls and a complex of buildings which point to the site being used as a royal residence by Dumnonia's kings. Coincidentally (or not!), Tintagel is precisely where legend states that Arthur was born, the fifth century 'battle leader' of the Britons.

Modern Devon formed the heartland of Dumnonia, with the county's name being a contorted version of 'Dumnonia' itself. During Britain's confused dark age period between the fifth and eighth centuries, 'Dumnonia' became mangled into 'Defnas', although this presents a problem. Given that the tribal name, Dumnonii, is broken down to provide a meaning of the 'masters, dominators', then how did it assume a completely different meaning? Simply put, that meaning may simply have changed over time.

Defnas is thought to mean 'deep valley dweller' (most appropriate for the Britons of Devon), but just who applied this meaning is unknown. Did the Dumnonii, the 'masters', simply become so associated with the Devon valleys that they in essence became the 'deep valley masters', and then the 'dwellers' of that region? The change in the name itself was likely to be the result of a consonant shift whereby 'dumnon' became 'defnon' and then became 'devon', perhaps aided by West Seaxe linguistic interference.

The eastern regions of Dorset and Somerset seem largely to have fallen at the same time as the AD 577 defeat of the three cities under the leadership of Caer Gloui. Following that they were settled by the Dornsaete and Somersaete Saxons while Dumnonia shored up its own defences to the south. Defnas itself fell to the West Seaxe between 652-685 (after which the deep valley masters were anything but masters), while the Cornish remnant of the kingdom was still fully independent until 875. Dumnonian independence lasted longer in its colony across the English Channel, in Domnonia.

Roman Canterbury

(Information by Peter Kessler, with additional information by Edward Dawson and Geoffrey Tobin, from The Landscape of King Arthur, Geoffrey Ashe, from Roman Britain: A New History, Guy de la Bédoyère, from Wessex, Barbara Yorke, from the Imperial Gazetteer of England and Wales, John Marius Wilson (1870-1872), from Making Anglo-Saxon Devon: Exeter, Robert Higham (2008), from History of the Kings of Britain, Geoffrey of Monmouth, from the Historia Brittonum (The History of the Britons), Nennius, and De Excidio Brittaniae et Conquestu (On the Ruin of Britain), Gildas (both J A Giles, Ed & Trans, 1841, published as part of Six Old English Chronicles (Henry G Bohn, London, 1848)), from the Annales Cambriae, James Ingram (taken from the Harleian manuscript, the earliest surviving version, London, Everyman Press, 1912), from The Anglo-Saxon Chronicles, Anne Savage (translator and collator, Guild Publishing, 1983), from A History of the English Church and People, The Venerable Bede (Leo Sherley-Price translation - revised by R E Latham), from The Age of Arthur, John Morris, and from External Links: Encyclopaedia of Earth, and the Cornwall Archaeology Society, and Early Christian to medieval settlement and cemetery (Historic England).)

c.290 - c. 305

Caradoc / Caratacus / Caradocus

Trusted advisor of Eudaf Hen of Ewyas. 'Duke of Cornwall'.

3rd century

The hill fort of Cadbury-Congresbury, close to Yatton in North Somerset, is occupied. It is the only major fortification in the south-west (and in Wales) to produce reasonable evidence for continuous occupation between this period and the sixth century.

Ipplepen Romano-British cemetery site
The Romano-British cemetery site at Ipplepen has revealed fifteen burials (so far) and a surprising level of continuity of use for a site in the south-west, which is normally more reluctant to reveal details of settlement occupation

However, a Roman cemetery which lies along the Roman road at Ipplepen in Devon, near Exeter, remains in use for up to three hundred and fifty years after the end of direct Roman administration of Britain.

In 2015, archaeologists unearth fifteen skeletons, a surprise to them which makes this one of the most important burial sites known in the region. The bodies suggest that life continues as normal at the settlement at Ipplepen, indirectly supporting the idea that a strong authority exist in the region which remains unaffected by events farther east.

fl c.300

Mauric / Meurig

First son. Heir, but predeceased Caradoc.

fl c.305

Donaut / Dionotus / Dynod

Brother. 'Duke of Cornwall'. Son-in-law, Conan, picked as heir.

308 - 313

Another Roman milestone is placed in the Tintagel area in the north of the Cornovii region, inscribed with the name Imperator Caesar Gaius Valerius Licinius Licinianus. He is promoted to Eastern Roman emperor in AD 313, thereby narrowing down the period of his reign in which the stone could be inscribed.

Other, uninscribed, milestones are also placed during the Roman period. One of these is near the hill fort at Carn Brea, another is close to Tintagel (Trethevy - see AD 251,above), and two more are close to St Michael's Mount (outside Penzance).

Sequential Maps of Roman Britain AD 43-425
Magnus Maximus revolted in 383 and invaded Gaul with a large army, but in preparation he is credited with setting up client kingdoms in Wales to protect the west coast from Irish raiders (click or tap on map to view full sized)

c.340 - c.387

Conan Meriadoc / Conanus

King of Vannetais. Left Dumnonia to his eldest son by Ursula.

337 - 343

The death of Roman Emperor Constantine, and then the death of his eldest son, Constantine II, in battle in AD 340 proves serious for Britain. Its early fourth century age of peace and prosperity begins to vanish.

Constans makes a sudden and very unusual visit in early 343 and it is also suggested that the widespread refortification of cities which occurs in this century happens as a result of this visit. Units of Germanic laeti begin to appear in some cities, notably Venta Belgarum in the Belgae civitas, and a steady trickle of migration begins from south-western Britain (notably the former territories of the Cornovii and Dumnonii) into Armorica.


Around this time, stones recording building or repair work appear along Hadrian's Wall. The stones are undated, but are placed in the mid-fourth century and two of them record work by the civitas Dumnoniorum and the civitas Durotrigum.

They seem to represent either an enforced labour party under military supervision (which would not discount the possible presence of a semi-independent Dumnonia), or the provision of civilian labour to maintain the country's defences (which still does not mitigate against semi-independence).

Magnus Maximus coin
The reverse of this coin issued by Magnus Maximus during his reign as co-emperor shows him standing, holding a laburnum and Victory on a globe


This is the minting date for the last Roman coins to be found in Dumnonian territory, showing that the region is still integrated into established Romano-British society at this time. This is also the approximate date at which the forum and basilica at Isca are given a new floor, showing that rebuilding and repair work is still taking place in Roman Britain. Unfortunately, the buildings are demolished within a generation.

383 - 388

Magnus Maximus, military commander in Britain, is credited by Geoffrey of Monmouth with setting up Conan Meriadoc as king in Armorica at the start of his own campaign to become emperor. Conan is the rebellious nephew of Octavius, Maximus' predecessor and one of the most important figures in Britain, so this could have an element of getting him out of harm's way in Britain.

FeatureThe relationship could make Octavius the father of Maximus' wife, as Conan is also her cousin. Conan's son, Gadeon, is mentioned in the Dream of Macsen Wledig (as his brother, Adeon - see link, right).

It may be the case that the estimated dates used here for Conan are a little adrift, and the earlier date may even represent a date of birth rather than the beginning of his reign, as a reign of forty-seven years seems a little long. By AD 388, as a result of Maximus' defeat, a large number of his surviving troops appear to return, but to settle in Armorica rather than Britain.

Glomel in Brittany
The landscape of Armorica - extremely hilly inland with a wonderful, long coastline - would have seemed very familiar to the Britons who began to settle here from the late fourth century onwards (Glomel in the modern Côtes-d'Armor département is shown here)

c.387 - c.390

Gadeon / Cadfan / Adeon

Son or brother. Half brother Erbin ruled Vannetais.

c.390 - c.400

Guoremor / Gwrfawr / Vorimorus

Son. Probable first independent king of Dumnonia.


By this time, Dumnonia has probably extended the territory under its control to include the former lands of the Durotriges in neighbouring Dorset to the south-east. The apparent lack of centralised tribal control in Dorset prior to the Roman invasion may be to blame for this, along with the massacre of the hostile nobility there, with no Durotrigan state now able to re-emerge when central control is apparently waning. Dumnonians are also to be found settling a section of Armorica which they name Domnonia.

However, it is during this new century that the Dumnonians finally abandon Isca (Exeter). Archaeology has shown a clear break in occupation around this time, with even renovation work which had been carried out on the Roman forum around AD 378 having been abandoned when the buildings are destroyed, presumably very recently.

If the Dumnonian leadership relocates to a single specific site then it may be Tintagel (in Cornwall). In 2016 the Cornwall Archaeology Unit begins a fresh dig there to discover walls about a metre thick.

Archaeology has established (from 2016) that Tintagel was the home to a privileged elite which was living a good life in a dense and complex settlement area behind strong stone walls - and perhaps not coincidentally, legend has long stated that it was here that Arthur of the Britons was born

The settlement area is discovered to be a dense one, with a complex of buildings, and large amounts of pottery from the eastern Mediterranean used for olive oil and wine, as well as Merovingian glass and fine Phocaean tableware from the west coast of Anatolia.

The people here are clearly well-off, and are maintaining old trading links with the Mediterranean and establishing new ones with the Franks via traditional markets in Gaul. No other, similar sites have yet been found for this period, so it seems possible that this is a permanent Dumnonian capital.

c.400 - c.410

Tutwal / Tudwal

Son. Probably m Gratianna, youngest of Maximus' daughters.

c.410 - c. 435

Marcus Conomari / Conomor / Cynfawr



Marcus Conomari (or Cunomorus) is likely to be the name inscribed on stone and later found between Castledore and Fowey in Cornwall. The likeliest translation of the Latin inscription is 'Here lies Drustan, son of Cunomori'. He is cousin to Anblaud of Ercing.

Speculation ties Drustan with Tristan, of Lyonesse and of the Arthurian story, Tristan & Iseult, which relates events during the reign of Cyn-March ap Meirchion of Cornubia. In the Life of St Pol de Leon, completed in 883, the king is referred to as 'King Marc whose other name is Quonomorus', or Cunomorus, meaning 'hound of the sea'.

Dumnonia in Maps - Map 2 c.AD 400
By this time, Dumnonia had probably extended the territory under its control to include the former lands of the Durotriges in neighbouring Dorset (click or tap on map to view full sized)


A theory by Dr John Morris, not fully accepted by modern scholars, is that there are two periods in this century in which elements of the Cornovii of the Midlands are moved into the south-west of Britain.

FeatureAccording to the theory, around this time, the leading nobles of Viroconium move to Dumnonia, transplanting their Cornovian name to the western peninsula (Cornubia) and ruling over the Dumnonians (King Constantine of circa 530 is unflatteringly described by Gildas (see feature link) as a 'tyrant whelp of the filthy lioness of Dumnonia', although this provides no suggestion that he may not himself be a Dumnonian).

While this theory has many detractors, there does seem to be a tradition of the Cornovii nobility joining that of the Dumnonians, and there is not nearly enough evidence to prove that this nobility is from Cornubia. Perhaps instead it represents a unification of two major and fairly powerful bodies in a location in Britain which offers more safety and better protection than the vulnerable West Midlands, or perhaps it merely covers the migration of a warrior elite, leaving the ordinary citizens behind it.

c.435 - 443

Constantine Corneu 'of Cornwall'

Son. Divided the kingdom between his two sons.


There is a (probable) Irish presence at Dunster Castle (Dindraithov or Dindraethou to the Welsh) in the early post-Roman period. This is a fort which overlooks the approaches to Exmoor, four and-a-half kilometres to the south-east of Minehead in Somerset (well within Dumnonian territory).

The modern castle may not be the same site as the post-Roman fort, which could be located a little way inland. Irish settlers are frequenting Somerset at this time, which suggests that they are a people who have already been accepted into Britain, such as with the Déisi of Dyfed.

Marloes Sands
The coast of Pembrokeshire, part of the territory of the Demetae and the later kingdom of Dyfed, is a mixture of sandy beaches and daunting rocks (as at Marloes Sands, shown here), but there would have been many places for the Déisi to land and seize some territory

FeatureThey are not large in number but they do remain for a long time. Nearby Glastonbury is spoken of as 'Glastonbury of the Gaels' thanks to its shrines of St Patrick and St Brigit. The fort features in the list of twenty-eight cities of Britain in Nennius' Historia Brittonum, appearing as Caer Draithou (see feature link), and is mentioned in the Life of St Carannog (of Ceredigion).

443 - c.480

Urban / Erbin ab Custennyn

Son. Abdicated in favour of Gerren before 480.

443 - c.510

Cornubia is governed as a sub-kingdom by Erbin's younger brother, Merchion. Upon his death, the region is further sub-divided to create an independent Lyonesse.

c.480 - 508

Gerren / Gereint Llyngesog ab Erbin

First son. Served with Arthur? Died at Portsmouth in 501?


Gereint ab Erbin (otherwise known as Gerren or Gerontius) features in the Arthurian story of Culhwch and Olwen. He is an important character in Arthurian literature, and is probably the brother of Veneva (the Romano-British form of Guinevere), who marries Arthur.

FeatureArthur himself is dux Britanniarum and possibly even an emperor of Britain in the style of several Romans before him. It seems reasonable that he would find a home in the land of his wife, at Cadbury Castle (especially given his own, traditional, origins in more-distant Armorica, and see feature link for a list of possible historical identities for him).

Cadbury Castle
Even today, Cadbury Castle presents the image of a powerful and defensible location, with views across the whole of Somerset giving it a level of strategic importance


FeatureAccording to tradition, Cerdic and his (young) son Cynric, together with Saxon and possibly some Jutish companions, land in five ships on the south coast of Britain at Cerdices ora, and begin a takeover of the local Jutish, Saxon and sub-Roman territories. Jutes and Saxons who are already settled there are apparently already referring to themselves as the West Seaxe (see feature link).

Geoffrey Tobin suggests that this 'landing' of 495 be taken literally. The Encyclopaedia of Earth states 'Tidal streams in the eastern English Channel and [around the] Channel Islands area [are] generally anti-clockwise, whilst the western entrance of the Channel has a clockwise tidal circulation [which is] wedded to the Celtic Sea'.

When visualising this, one can expect frequent landings in Hampshire both from Brittany and Flanders by skirting the English coast, and return journeys to the Cotentin peninsula then passing along the coasts of Brittany and France.

Cerdic may take one of these routes while the Saxons take the other. If the strong states of Domnonia and Dumnonia are in fact a single kingdom in the fifth century, and Cerdic is an ambitious noble, perhaps a fractious younger brother of the magistrate or governor of this region, then this would explain his actions in landing near Southampton (as Bretons later often do) and taking on the loyalist Natanleod (in 508 - assigned to Caer Gwinntguic for ease of reference).

Map of Britain AD 450-600
This map of Britain concentrates on British territories and kingdoms which were established during the fourth and fifth centuries AD, as the Saxons and Angles began their settlement of the east coast (click or tap on map to view full sized)

Having established a beach-head, it would reflect the times for Cerdic to forge alliances with rebellious Britons, immigrant Saxons, and hybrid groups who need a seasoned battle leader to lead them.


FeatureA newly arrived Saxon chieftain and his two ships of followers kill a Briton of very high rank at Portesmutha (British Portus Adurni, modern Portchester near Portsmouth - see feature link). This is possibly the last surviving part of the proposed British kingdom of Rhegin, but the Briton could also be Gereint of Dumnonia despite the apparent incongruity in dates (all dates for this period are flexible anyway, being handed down by tradition, or being estimated based on existing records and knowledge).

Dywel ab Erbin

Served with Arthur? Died c.520? Son possibly St Pirran.

c.508 - c.530

Cado / Cato / Cadwy ab Gerren

Son of Gerren. King of Dumnonia & duke of Cornubia.


The line of sub-kings in Cornubia appears to die out, so the region seemingly passes back into Dumnonian hands, with a 'duke' of Cornubia nominally governing the land. The first of these, Cado, may be the Duke Cador of Cornwall of Geoffrey of Monmouth. It is probably this Cado who is mentioned in connection with Arthur in the Life of St Crannog (of Ceredigion).

Duke Gorlois and Igraine
Duke Gorlois of Cornwall (Cornubia) and his wife, Igraine, as depicted in the illustration for Warwick Deeping's 1903 work, Uther and Igraine

Iestyn / St Justin

Brother. Entered the Celtic Church.

Selyfan / Solomanus / St Selevan

Brother. Entered the Celtic Church.

St Breage

Sister. Entered the Celtic Church.

c.530 - c.560

Custennin ab Cado / St Constantine

High king of Britain until c.540. Entered monastery. Killed 589.


FeatureConstantine is one of the kings attacked by Gildas in the monk's work, On the Ruin of Britain, probably indicating his fame as one of the more powerful of his peers at this time. The king is referred to as a 'tyrant whelp of the filthy lioness of Dumnonia' (see feature link). The 'filthy lioness' may be a less than flattering reference to his mother.


According to William of Malmesbury, Cyndrwyn Glas settles in the Dumnonian region of Glastenning with his livestock after finding it deserted, migrating there from Luit Coyt (an early connection to this place in Pengwern which will later become important to him and his offspring).

Cyndrwyn Glas appears to be a king or sub-king here, and there is also a Cyndrwyn Fawr who appears as a ruler in Pengwern around 613. Given the links between the Dogfeilion kings and Pengwern, this could also be Cyndrwyn Glas. 'Fawr' means 'great' in Brythonic/Welsh, suggesting that he has built a reputation for himself. Could he also be Cyndrwyn 'the Stubborn' of South Powys?

The Glastonbury region seems to have experienced a power vacuum in the mid-fifth century which allowed the Dogfeilion to walk in and take over - or be appointed there, perhaps

c.560 - 598

Gerren rac Dehau 'for the South'

Son. Fought the Bernician Angles at Catreath.


FeatureOnce the West Seaxe make the breakthrough of capturing Caer Baddan, Caer Ceri, and Caer Gloui, Glastenning and the heartland of eastern Dumnonia are under direct threat. However, it seems likely that the three cities had been receiving military support from Glastenning or Dumnonia, and one of these two kingdoms holds onto the West Wansdyke territory after their fall.

Both are now cut off from any overland contact with any other British territory. Cadbury Castle is also abandoned around this time, perhaps suggesting an evacuation of its occupants.

The Hwicce soon migrate into the northern remainder of the territory of the three cities while Caer Baddan is inhabited by the Saxons of the Somersaete who retain the name, but pronounce it as Bathanceaster (the city or fort of Bathan). In time it becomes the city of Bath.

Dumnonia in Maps - Map 3 AD 577
When the West Seaxe removed the entire area between Gloucester and Bath of British resistance in AD 577, the West Wansdyke appears to have remained in British hands (click or tap on map to view full sized)

598 - 613

Blederic / Bledric ap Custennin

Brother. Killed at Battle of Bangor-is-Coed by Æthelfrith.

597 - 611

The West Seaxe under Ceolwulf force the Dumnonians out of the West Wansdyke region of Caer Baddan (Somerset). However, it is around this time (in the early years of the seventh century) that the Britons of Glastenning found Glastonbury Abbey.

The fact that they are able to do this means that the West Seaxe conquest of the West Wansdyke has not proceeded particularly far south, and Glastonbury is still in British hands. The island of Beckery in the nearby Avalon Marshes has already provided a monastic home for the British Church since the late 400s.


Bledric ap Custennin dies at the Battle of Bangor-is-Coed, which follows very soon after the British defeat at Caer Legion (Chester). In fact, a great many British leaders have been killed over the course of the two momentous battles, and a power vacuum appears to allow the Dogfeilion kings to secure the Powysian throne.

FeatureThe monks of Bangor-is-Coed are present at the battle to pray for divine support, but they too are slaughtered (the act is seen as divine retribution for their refusal to help evangelise the English in 603 - and see one of Geoffrey of Monmouth's more accurate entries about this campaign via the feature link).

Hinton Hill in Somerset
Hinton Hill lies near the village of Wellow in Somerset, and in 577 it was the site of the Battle of Deorham between the allied free Britons of the three cities of Caer Baddan, Caer Ceri, and Caer Gloui and the invading West Saxons (External Link: Creative Commons Licence)

613 - ?

Clement ap Bledric



Cynegils of the West Seaxe takes advantage of Bledric's death in battle, and the accession of his son, by invading Dumnonia. Badly defeated at the Battle of Beandun (probably Bindon, immediately east of Axmouth in Devon), Bledric's son, Clemen, is forced to retreat back to Caer Uisc (Exeter), where archaeology suggests that a major Roman building is still being occupied into the seventh century.

Possibly, this incursion weakens the Dorset and Somerset regions of the kingdom so that independent groups of Saxons are able to make inroads over the next generation, forming the Dornsaete and Somersaete respectively.

fl c.630

Petroc Baladrddellt ap Clemen

Son. 'Baladrddellt' is the 'Splintered Spear'.


Cenwalh of the West Saexe makes a breakthrough against the Dumnonian defensive lines at the battle of Bradford-upon-Avon. This means they make use of the gap in the Wansdyke caused by the passage of the River Avon. The Dornsaete (Dorset settlers) who have been slowly pushing against the Dumnonian borders now come under West Seaxe control whilst Dumnonia loses more territory to the invaders.

Dumnonia in Maps - Map 5 AD 652
The West Saexe made a breakthrough against the Dumnonian defensive lines at the battle of Bradford-upon-Avon in AD 652, managing to work their way through the Wansdyke defences (click or tap on map to view full sized)

bef 658 - af 661

Culmin / Cwlfyn ap Petroc

Son. Defeated at the Battle of Peonna.


The West Seaxe are victorious at the battle of Peonna (Penselwood - the densely forested area on the eastern boundary of Somerset), and the Dumnonian forces are put to flight to the River Parrett.

The eastern half of Dumnonia is permanently captured by the Saxons as they advance through the Polden Hills to the new border of the River Parrett (approximately forty-five kilometres farther west). They may even go further than this, to the hills which separate Somerset from Devon, as place names suggest settlement well before the end of this century.

FeatureThe Brito-Welsh territory of Glastenning (in modern Somerset) is probably taken at the same time. The Somersaete also now come under West Seaxe control (if they hadn't already after 652), as does Glastonbury Abbey (see feature link), which is allowed to retain its British abbot.

The fifth or perhaps sixth century construction of the Wansdyke was a massive undertaking which reached from west of Caer Baddan's capital (Roman Aquae Sulis, modern Bath) to the proposed north-western corner of Caer Celemion's border, all to the north-east of Dumnonia's border (External Link: Creative Commons Licence)


An Easter battle is fought at Posentesbyrig - which could be the Iron Age hill fort at Posbury, just three kilometres to the south of Crediton (immediate west of Exeter in Dumnonia). The result of the battle is not recorded but, assuming a West Seaxe victory, this would give them control of the fertile lands of the Exe and Creedy valleys.


Æescwine of the West Seaxe fights the battle of Biedanheafde (later Bedwyn, possibly Crofton but the actual location is debatable) against Wulfhere of Mercia. Æescwine repels the Mercians but is unable to gain any advantage from it.

The Mercians in this period are a serious threat to the West Saxon hold over their northern provinces, and to maintain their prestige and revenue, they compensate by continuing to push hard against the borders of Dumnonia to the west.

FeatureThe renowned West Saxon missionary to Continental Europe, St Boniface, is born just outside the recently-conquered Crediton (in Devon) around this date, and later receives an English education in a monastery at Exeter (see feature link), which is conquered by the West Seaxe around 685.

Dumnonia in Maps - Map 6 AD 658
In AD 658 the eastern half of Dumnonia was permanently captured by the West Seaxe as they advanced through the Polden Hills to the new border of the River Parrett. They may have gone even farther than this (click or tap on map to view full sized)

fl c.682

Dungarth ap Culmin


681 - 685

The West Seaxe conquer the remainder of Somerset as Centwine clears the western coastal area as far as the Devon border. In a two-pronged attacked the territory of the Defnas (Dumnonia / Devon) Britons is also taken by an army which presses along the English Channel coast from Dorset to Exeter.

This also serves to confirm that Dorset has fallen to the Saxons (see Map 7 of the Dumnonia map series by clicking or tapping on one of the maps above or below).

Amusingly, it seems the new masters of Somerset ask the Celtic natives for the name of a range of hills to the far west of this region. Rather than a name, they are given the Brythonic plural word for hill, 'brendo', to which the Saxons add their own word, 'hill'. The area becomes the Brendon Hills of Somerset, literally the 'hills hills' (the same thing happens with many rivers, the Brythonic 'afon' meaning 'river', so that the many River Avons are literally the 'river river').

bef 700 - 710

Gerontius / Gerren ap Dungarth

Son. 'King of the Welsh'. Defeated & killed by Ine of Wessex.


Ine of the West Seaxe defeats and kills Gerren inflicting another defeat on his British neighbours to the west. This victory seems to bring West Seaxe domination to the line of the River Tamar, limiting the Britons to Cornwall.

The various versions of the Anglo-Saxon Chronicle (ASC) label Gerren 'the Welsh king', and some published compilations fail to list the battle's outcome. Twelfth century chronicler John of Worcester - with access to versions of the ASC which have not survived to the present day - states that Gerren is killed.

Dumnonia in Maps - Map 8 AD 710
In AD 710 the West Seaxe made their big breakthrough when Ine defeated and killed Gerren of Dumnonia, inflicting another, very heavy defeat on his British neighbours to the west (click or tap on map to view full sized)

c.710 - c.715

Ithel ap Dungarth 'the Rock'

Brother. Probably ruled. Line continues with Dyfnwal, below.


From this point onwards, the descent of the kings of Dumnonia becomes highly unreliable, as the kingdom is slowly crushed by Wessex. Ithel's immediate successor is not known, unless it his son who is thought to be active in the 730s.

Even this son, Dyfnwal, cannot be confirmed as king. His name, and that of his successors, is mentioned only in the Book of Baglan, a collection of Welsh manuscripts which is compiled in 1600-1607. These names are shown below in green to differentiate them from kings who are known from other sources.


FeatureThe Annales Cambriae (see feature link) refers to three notable 'Cornish' victories (dated tentatively to this year). The opponent is not named but, as the 'Britons were the victors in those three battles', the opponent is clearly the West Saxons. The battles take place at Hehil, Garth Maelog, and Pencon (Pencoed).

The first has been the subject of much speculation as to its location, with many scholars taking the mention of 'Cornish' too literally and placing it west of the River Tamar. Instead, all three battles are likely to be in what is now Devon, close to Dumnonia's eastern border - the West Seaxe would regard all free Britons in this area as Cornish by this date, whether or not they live to the west of the Tamar, whilst the Annales Cambriae states that the second and third battles take place amongst the 'South Britons'.

River Tamar
The mighty River Tamar remained a barrier to travel even in the nineteenth century - until the coming of the railways - but in the eighth century it formed a vital line of protection for the remnants of the Dumnonian kingdom

The victories are hugely important, as they appear to win the Dumnonians and Cornish a century of peace in which to cement their compressed but surviving kingdom, and possibly ensure the survival of their culture and language much longer than might otherwise be the case.

One has to wonder how far the victories allow the Britons to penetrate into occupied Devon - they do seem to recover parts of Devon as evidenced by the West Saxon attack on these parts in AD 814.

FeatureAlso, in the same year of 722, Queen Æthelburg of the West Saxons destroys the fort at Taunton (see feature link for more on the castle on this site). Could this be to prevent it being captured by attacking Britons?

Archaeological evidence at Carhampton in West Somerset further supports a sudden and urgent withdrawal by Saxons from the region in this century, with metalworking sites being abandoned suddenly (see the Historic England link in the sources, above).

fl c.730s

Dyfnwal Boifunall ap Ithel

Son. Dyfnwal of Boifunall.


The Romano-British cemetery at Ipplepen near Exeter in Devon falls out of use around this time, some three hundred and fifty years after the official end of the direct Roman administration of Britain. The surprising level of continuity of use up to this period seems to support the picture of Devonian Dumnonia being largely unaffected by the turmoil to the east, but it also backs up a picture of a kingdom which is now being compressed by the West Saxons.

Dumnonia in Maps - Map 9 AD 722
The victories of AD 722 were hugely important, as they apparently won the Dumnonians a century of peace, and may even have penetrated far into Devon - a West Saxon attack of AD 814 seemed to aim at the recovery of these regions (click on map to view full sized)

By the end of the century, the independent Britons of this region are pushed back to the Tamar, placing Devon in Saxon hands (this time without hope of the Britons regaining them).

fl c.750s

Cawrdolli ap Dyfnwal


fl c.770s

Oswallt ap Cawrdolli

Son. Bearing an English name.


Oswallt's name is a Saxon one in British form - 'Oswald'. Could he be Saxon, or part Saxon, or is it now becoming 'trendy' to adopt Saxon names for British offspring? Another explanation is one of safety. The appearance of adopting English names could be an attempt to convince the English that the Cornish are trying to fit in with the new order and therefore be spared to retain their semi-independence. Oswallt's son, Hernam, is probably the Saxon Herman.

FeatureDespite apparently adopting English names, it is again recorded by the Annales Cambriae (see feature link) that the 'South Britons' of Dumnonia suffer devastation, this time at the hands of Offa of Mercia. This Bretwalda rules all of southern Britain with a level of aggression which is typical of the hard-fighting Mercian kings. This appears to be the final mention of the 'South Britons' in Welsh records.

fl c.790s

Hernam ap Oswallt

Son. Bearing an English name.

c.800 - 875

The kingdom of Dumnonia, so compressed by the inroads made by Wessex, effectively ceases to exist during the ninth century. The remaining British territory is known as the kingdom of Corniu (or variously, Cerniu, Cernyw, or Kernow). The English know it as Cornwall, meaning 'the Welsh of Corniu'.

Dumnonia in Maps - Map 10 AD 802-825
The Dumnonian victory of AD 722 seems to have remained largely unchallenged for almost a century, but in the early ninth century the West Saxons made a series of devastating advances of their own (click or tap on map to view full sized)

During this century the absorbed Britons and newly-arrived West Saxon settlers in Dumnonia's lost lands begin to appear in written form, pre-dating the appearance of the shires into which they will eventually be assigned.

The Wilsaete are mentioned in 802, the Defna, the 'men of Devon', in 825, the Dornsaete in 940, and the Somersaete in 845. The Dumnonian city of Isca is referred to by the West Saxons as Exan-Cestre or Exacestre, meaning 'the fortified city of the Exe'. Over time the name passes through several variations - Exceaster, Excester, and Exceter - and finally (for now) Exeter.

fl c.810s

Hopkin ap Hernam



Ecgberht of Wessex invades and subdues parts of Dumnonian Devon. Clearly the 'destruction' by Ecgberht of Dumnonia in 802 is not as serious as has been recorded. Have some Devonian Dumnonians staged a revolt?


The men of Cornish Dumnonia clash with the West Saxon commanders of Devon at the Battle of Galford (alternatively shown as Gafulford, Gafulforda, Gafolforda, or even Gavelford). This is the first written record of Devon to show it using the Saxon form of the name.

Taunton Castle
Ine's fort at Taunton has long gone, and the present Taunton Castle - which houses the Museum of Somerset and which itself underwent various stages of development - does not stand on the same spot, but was the original destroyed by Queen Æthelburg in the face of a victorious Dumnonian advance in AD 722? (click or tap on image to read more about this castle)

The actual site of the battle is somewhat disputed but recent writers have tended to select Galford on the River Lew in Devon, a possible border point at which taxes could be collected for cross-border trade (Robert Higham points out the fact that Gafol-ford means 'tax, tribute ford').

fl c.830s

Mordaf ap Hopkin


833 - 870

At some point between these dates, during the incumbency of Ceolnoth as archbishop of Canterbury, the independent Cornish bishops submit to the English church. Corniu is included within the diocese of Sherborne. The first bishop of Cornwall is Kenstec.

fl c.850s

Fferferdyn ap Mordaf


c.865 - 875

Dunyarth / Doniert / Dungarth / Duncan

Possibly a descendent of Gerren. Drowned.


Dunyarth is traditionally said to be the 'last king', and is mentioned in Annales Cambriae as having drowned in 875. By this tragic event Dumnonia can certainly be said to be extinguished.

Land's End in Cornwall
Land's End in Cornwall, like the rest of this duchy never actually part of England, but certainly neighbouring it and, in the twenty-first century, a thriving tourist hotspot

Wessex already controls most, if not all, of Devon up to the River Tamar. The remaining free Britons of the south-west maintain their independence on the western side of the river, in Corniu, which is where any subsequent Dumnonian history is recorded.

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