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Post-Roman Britain

Early Independent Britain AD 400-425

by Peter Kessler, 1 April 1999. Updated 16 February 2019

The well-known date of Britain's final official break from Rome is AD 410, but by that stage Roman Britannia had mostly been fighting its own battles for at least thirty years with only occasional support from Rome itself. It was forced to look after its own interests in the face of increasing numbers of barbarian raids; from the Picts to the north, the Scotti (Irish) to the west, and from various Teutonic tribes which were raiding to the south and east of the country.

There had been frequent barbarian raids throughout the latter part of the fourth century in Britain. The 'Barbarian Conspiracy' of 367 was a threefold attack by Teutons from across the North Sea, and Picts and Scotti from the north and west. It's impossible to know how well coordinated these attacks were - or whether they were coordinated at all. The attackers kept no records of their own at this time and even Roman records of this period are sketchy as the imperial system was gradually breaking down.

Magnus Maximus

The next crisis faced by Britain came in 383 when the military commander, Magnus Maximus, realised that Roman power in the region was becoming increasingly toothless. He made his own claim for imperial power, supported by the army. His death in 388 deprived the island of the greatest part of its military strength, although the reorganisations usually attributed to him shored up the north and the western coasts of Britain. However, there appears to have been almost continual warfare against the Picts during this period.

Around 398, Britain apparently had to be rescued from her barbarian foes, this time by the most powerful general of the Western Roman empire, Stilicho. Stilicho's intervention was the last occasion on which a major expedition was mounted against the enemies of Britain.

Soon after the situation had been retrieved, Roman forces on the island were further reduced to save Italy from invading Goths. By 406, Britain's military strength had largely been drained away, and the following decade saw the process completed.

In 406 a vast army of barbarians crossed the frozen Rhine and began advancing westwards towards the Channel coast. It began to appear as though Britain could be invaded.

Constantine III

Earlier in the same year, the army in Britain had already elevated an unknown soldier, Marcus, to supreme power. He did not last long, being supplanted at the time of the barbarian advance through Gaul by Gratian, an urban magistrate (magistratum). Gratian survived only four months, and the army's next choice fell on a soldier, Constantine, who challenged Roman authority in Gaul, creating a prefecture at Arles from which to rule as Emperor Constantine III.

Constantine had, in 407 removed at least something of Britain's remaining trained forces only to be killed in 411 at Arles. The troops never returned but instead may largely have settled in Armorica, paving the way for later British migrations there.

In 408/409, Britain was subjected to a large-scale barbarian invasion, probably by Saxons with Anglian support.

The British civitates - the urban centres - managed to defend themselves and by 409 had quelled the attack, although details of how they did this are not available. It is possible that many of the surviving defeated Saxons and Angles were employed as foederati - mercenary troops - to garrison the Saxon Shore (the east coast) and protect it from further attacks. Although this was established Roman practise, and was undoubtedly in use before this time, this action would help to explain the large number of Teutonic sites along Britain's east coast which are evident from before the so-called Adventus Saxonum in 450.

Abandonment by Rome

The Roman city of Bath

Roman Bath, one of the best-known cities which was a neighbour of the provincial capital of Corinum (click or tap on image to read more on a separate page)

In 410, the feeble Emperor Honorius informed the internal government of Britain that it would have to look after its own defence, implying that this would be a permanent arrangement. During what was either a revolt of peasants and slaves in Britain in 409 to mirror either the popular uprising of the oppressed classes in Armorica (Brittany), or at the tail end of the barbarian invasion, the Romano-British governor had appealed for imperial help.

In the face of this abandonment by Rome (although there is much more to this story and its background - see The End of Roman Britain), the defence of Britain was left to the western and northern kingdoms and whatever remained of the central government. In the eyes of the traditionalist Celts of the wilder north and west, the leading figure of this central authority would probably have fulfilled the traditional role of high king of Britain - if such a title ever actually existed. To his Romanised peers he could have been known as emperor of Britain in the Roman fashion, at least while such a title still meant anything.

Theoretically, Vortigern could have been the first of these purely internal emperors, with Ambrosius Aurelianus and Arthur following them (Uther Pendragon is harder to pin down, but would have governed between Ambrosius and Arthur unless, of course, he was in reality the same person as Ambrosius, an argument not within the scope of this feature).

Border client kingdoms

Welsh tradition has long held that Magnus Maximus arranged the island's defences before undertaking his expedition abroad to claim the imperial title. Other sources attribute some of the changes to Vortigern, so a combination of the two is highly likely. Magnus Maximus, though, clearly seems to have begun the work and seems likely to have made the greatest number of changes. What he apparently did was to arrange large defensive areas which could be governed by client tribes or native Roman officers.

All of these were set up in the militarised zones, in the west and north, areas which had never been fully Romanised and which had been under military control for years through several chains of forts. The borders shown in the map below are mostly conjectural, but are based on later kingdoms which emerged in these areas through the inevitable fragmentation which occurred when Celtic tradition demanded an equal distribution of land between surviving sons.

The south and east, areas far more greatly Romanised, came under the island's central administration for as long as it lasted. This explains the proliferation of early independent Celtic kingdoms in the west and north, while the heart of the Celtic 'Lloegr' (England) was much slower to fragment and, perhaps because of that, was a much easier area from which Angles and Saxons could grab territory.

However, kingdoms - or at least small city states - did emerge in the south and east, mostly towards the end of the fifth century. Some of these left evidence of their survival, if not their names. (Details of these can be accessed via the The Island of Britain. map.)

Map of Britain AD 400-425
The solid red which depicts Roman Britain began to fracture in the late fourth century, while the early fifth century saw it broken up almost entirely (click or tap on map to view full sized)


Ceretic Guletic, king of Alt Clut

Ceretic was the earliest-known ruler of Alt Clut (Strathcluaide) in this period, and perhaps the first to be recognised by Britain's central administration. However, it seems certain that the kingdom was created in AD 148, and possibly by a descendant of the last free high king of Britain, Caratacus. This was one of the 'four kingdoms of (Lowland) Scotland' which held the territory between 'proper' Roman Britain and the Pictish (British) north. Most of them may have maintained Roman client kingdom status for much of their existence before 409.

Ceretic ruled his territorium from the location from which the kingdom took its name, a rocky promontory overlooking the Clyde. This capital became known as the 'Fort of the Britons', Dun Breaton (and later, Dumbarton). Policing the western half of the Antonine Wall as a (probable) Roman client chieftain, Ceretic and his descendants forged a strong but poorly recorded kingdom which, alone amongst the British kingdoms outside Cymru, was never successfully conquered by the English. Instead, after becoming a Pictish/Scottish satellite state in the ninth century, it was fully merged within Scotland in the eleventh century.



Although Cunedda Wledig originated from the westernmost part of this region around the start of the Firth of Forth if, as per tradition, he was relocated by Magnus Maximus then he would have been in North Wales by 383. The first known ruler of Guotodin is Lot Lwyddog, who reigned around the end of the fifth century - before that there seems to be little information on this northern tribe and it is possible that the Votadini chieftains, late in accepting the benefits of Roman civilisation, were also late to unite and form a single political entity.

Nora Chadwick's The Celts theorises that Coel Hen and his descendants guarded this eastern end of the Antonine Wall, in the buffer zone between that and Hadrian's Wall. Could Coel Hen have commanded, as governor of the militarised zone of northern Britain, the Votadini chieftains, perhaps dealing directly with one high-chieftain? It seems highly plausible after the death of Ceneu ap Coel, Coel Hen's son, that the Votadini (Guotodin), would seek to emulate the kingdoms being formed by his sons to the south. As a kingdom, Guotodin may well have been created only by around 470, with Lot Lwyddog as its first ruler.

Unfortunately, the kingdom never had a stable line of succession, and after the rulers (a king and a probable sub-king) were defeated at Catreath around 597, as described in the Gododdin, the Guotodin were fatally weakened, and their remnants fell in 638 to the Angles of Bernicia.


[1] In his book, Roman Britain, Guy de la Bédoyère contests that the mention of Valentia in the Notitia Dignitatum is a transcription error which should instead say that the province of Maxima Caesariensis had been renamed Valentia, probably at the same time that London was renamed Augusta, after 367.

Coel Hen, governor of Northern Britain

The capital of late Roman Britain in the north was Eboracum, later Ebrauc to the British, Eorforwic to the English, and contorted into York by the Danes. This was the civitas capital of the Brigantian Britons who, as pre-Roman Celts, had ruled a huge swathe of central northern England in the early first century AD and probably before.

Archaeological evidence points to a period of rebuilding in York at the start of the fifth century, when Coel Hen was estimated to be at the height of his governorship of the region. But, formed partly it seems from the Roman military district of Valentia, the province of Northern Britain covered the whole of the Roman militarised zone from a line close to the Humber to Hadrian's Wall and a lesser sphere of influence for some distance beyond it (perhaps including the Votadini, as mentioned above). [1]

Quite possibly appointed to his position by the departing Magnus Maximus, Coel Hen was probably the last Roman-style dux brittanniarum, and he would have ruled in a very Romanised fashion. He held the north in a strong protective grip, and guaranteed that he and his immediate descendants had little trouble from the Picts to the north. Unfortunately, his descendants divided what was a very strong single political entity into a patchwork of small kingdoms which fell one by one to the Angles.


Cunedda Wledig, ruler of North Wales

The ninth century Historia Brittonum (The History of Britain, attributed to a certain Nennius) is the earliest source of Welsh history outside the Lives of the Saints. It records that a certain Cunedag (Welsh 'Cunedda'), together with eight of his sons and one grandson, came from Manau Guotodin (near the Firth of Forth) a hundred and forty-six years before the reign of Maelgwyn, king of Gwynedd, and that they had expelled the Irish forever from those lands.

This was the primary reason behind the decision to invite Cunedda to become 'King of North Wales' as he was styled (although this appellation probably came much later, after his lifetime - he was never referred to as rex, 'king', in the Historia Brittonum). Maelgwyn's reign began in 517 so this places Cunedda's migration at 371, which seems a little early. Magnus Maximus is usually credited with reorganising the country's defences leading up to his departure in 383, and it is this date which is more traditionally linked with Cunedda, so something between 380-383 seems more acceptable for the move.

Cunedda and his people quickly settled in Gwynedd, carrying out their task of expelling the Irish invaders who had begun to settle there. The process of 'freeing' North Wales seems to have lasted a few years, until the only remaining Irish stronghold was on Ynys Mon (the Isle of Anglesey). Signs of Irish settlement in the area can still be found opposite Irish Leinster, in the probable origin of the Lleyn peninsula - the long 'pig's ear' - as its name may contain Irish Laigin, meaning 'Leinstermen'.


Antonius Donatus Gregorius, ruler of South Wales

Antonius, also known to Welsh tradition as Anawn Dynod, was another alleged son of Magnus Maximus, set up in his own territorium either by his father or shortly after his departure. The positioning of Demetia, kingdom of the Demetae Britons, meant that it could protect the south-west coastline from Irish raids.

The South Wales region soon crystallised into the kingdom of Demetia, later Dyfed, and was made up of two main regions. The larger part of the territory was Dyfed itself, while Ystrad Towy (or Towi) made up the eastern third or so. This was conquered around 690 by Ceredigion, but Wales was united under the kings of Gwynedd in the ninth century, and Dyfed came to form the heart of a united South Wales after that, with Deheubarth being formed out of this union. The later kingdom of Brycheiniog also seems (at least partially) to have formed a division of the South Wales territory.

As a complete opposite of the process going on in North Wales at the same time, Irish settlement in Demetia was actively encouraged in the form of inviting the Irish Déisi tribe to settle there. They seem to have been brought in to act as foederati on the west coast, keeping the British shores clear of Irish raiders, an apparently successful policy. In the region, many Irish words are mixed into the regional dialect, and there is a considerable spread of memorial stones pointing to Irish influence. The incidence of Ogham (Irish) symbols, highest in the modern county of Dyfed, is a crude guide to the settlement of the Déisi. After the British line of rulers had died out, the Déisi were best placed through intermarriage to assume the legitimate rule of Dyfed.


Owain Finddu, ruler of Mid-South Wales (Cernyw)

Although many later Welsh kings claimed descent from Magnus Maximus in order to legitimise and enhance their own status, Owain Finddu has one of the better claims. His territory seems to have been created or founded to plug a gap between South Wales and Ewyas (on the western bank of the River Severn).

The kingdom of Cernyw emerged from this under the control of Owain's son, and was renamed after Owain's great-grandson as Glywyssing. Even later, in the tenth century, it was again renamed after one of its most powerful late rulers as Morgannwg, and is remembered as today's Glamorgan region.


Meirchion, ruler of Ewyas

Probably the great-grandnephew of Eudaf Hen (the Old), former king of Ewyas, Meirchion son of Gwrgant seems to have been the last ruler of Ewyas. The kingdom was without a ruler around 430, so that Vortigern was able to give it to his eldest son, Vortimer. Vortimer appears to have been able to claim the area as his inheritance through the maternal line as a great grandson of Eudaf Hen.

Ewyas as a distinct region seems to date from at least the late third century. It was situated at the very centre of what in the mid-fourth century became the Roman civil administration's province of Britannia Prima, stretching from Cornubia to North Wales and east to the Gloucester and Cirencester areas.


Vortigern, ruler of Pagenses / Paganes (Powys)

The Pagenses - perhaps more realistically Paganes - appears to have grown into a recognisable region and even kingdom only in Vortigern's time, so it is likely he was drawing upon territory which had previously come under Britain's central administration. This was part of his powerbase from which he was able to build his claim to be able to command all of Britain.

Philip Barker's painstaking years of investigation at Caer Guricon (Urecon, Roman Viroconium, modern Wroxeter), which was the part-military, part-civil civitas (tribal capital) of the Cornovii, revealed the construction well into the fifth century of a large and remarkable timber palace on quasi-Classical lines. Grandiose in conception, there existed a massive hall with a linear spread of outbuildings and even, perhaps, shops, all executed in timber. Once Pengwern had emerged as a separate region at the end of the sixth century, this became its early capital.

Vortigern's main powerbase seems to have been further south than Powys. His father may have had connections with Caer Gloui. Given the later divisions of towns in the area, Caer Baddan and Caer Ceri could also have formed part of this territory. From the available evidence it seems likely that, once Vortigern was defeated shortly after the civil war of the 440s, Ambrosius Aurelianus confirmed the rule of Vortigern's compliant sons over Powys, Builth, and Gwent, and took the Gloucester region to form his own powerbase in the south. Is it possible that the territories of Caer Gloui, Caer Baddan, and Caer Ceri all formed parts of one administrative region in the mid-fifth century, and that they were passed onto Ambrosius' descendants, to finally be conquered by the West Saxons in 577? It seems highly likely.


Vorimorus, king of Dumnonia

The Celtic tribe of the Dumnonii ruled a large kingdom which covered the whole of the West Country from Somerset onwards. It probably began to emerge as a distinct region by the beginning of the fourth century. It had become a fully independent kingdom by the fifth century, probably by 410.

In this area, scarcely touched by Roman occupation, the Dumnonian leaders would have exercised a far higher level of self-rule than many areas of Britain. They controlled a wide swathe of territory which also comprised the former territory of the Durotriges and the possible tribe of the Cornovii, in modern Dorset and Cornwall respectively.

As well as producing one of the earliest independent kingdoms south of Hadrian's Wall, Dumnonia was one of the most stable until the West Saxon territorial gains of the late sixth century, neither changing its name nor fragmenting in the way of most of Britain's Celtic kingdoms. It produced a few sub-kingdoms - Glastenning, Cornubia, and Lyonesse - which were ruled, in the same manner as Gwynedd, under Dumnonia's overall control, and were mostly later drawn back under direct rule. Glastenning was the only one not regained in whole, but this was due to Saxon conquests in the region.

In the remote south-west, the English name, 'Cornwall', derives directly from its Romano-British label. Its late Romano-British name, Cornouia, which was Latinised as Cornubia, has survived as Welsh Cerniw and Cornish Kernow (not to be confused with the Cernyw of Glywyssing). Cornubia seems to have constituted a pagus, a Roman subdivision, within the civitas of the Dumnonii and later, as stated, a sub-kingdom for a time before it was merged back into Dumnonia as the latter was being reduced by Saxon advances.


Dumnonia in maps

View a series of maps showing Dumnonia's existence between around AD 400 and its final extinction at the hands of the West Saxons (click or tap on image to read more on a separate page)

Flavia Caesariensis

Although the region illustrated on the map above existed as a late fourth century Roman civil administration province (borders conjectural but relatively acceptable), some older sources list its name as Britannia Secunda, and place Flavia Caesariensis as a very small province in the area of Carlisle in modern Cumbria.

By the late third century the whole south-east region was governed by the Comes Litoris Saxonici, 'Counts of the Saxon Shore', with an opposite number of equal rank controlling the north in the form of Dux Britanniarum, 'Duke of the Britons', the last of which was probably the Coel Hen (although like Arthur his existence and role are not fully accepted). The comes was charged with guarding the entire east and south coast, from the Humber to the Isle of Wight, from increasingly frequent raids by Saxons and Irish Scotti.

Many of the defended areas were settled with Teutonic foederati to strengthen native defences there. These forces may have greatly been increased after the barbarian raid of 408/409, when the Roman administration was expelled and the Britons had to look after their own defences. They eventually seem to have sided with mid-fifth century Teutonic arrivals to form the earliest Saxon and Anglian kingdoms in these regions.

It seems highly likely (although it is completely undocumented) that, if the south-eastern Roman provinces survived the AD 409 expulsion of Roman administration and its uncertain aftermath, then they probably survived until the middle of the same century. In that period, over the course of a decade, the country was ravaged by foederati revolt, plague, civil war, Pictish incursion, and Jutish invasion.


Maxima Caesariensis

The Romans were familiar with the Celtic tribal divisions in the country, and they accommodated this habit in their own organisational divisions. Britain (England and Wales) is a relatively small country, but then as now it is still too large and diverse to administer as a single entity.

Britannia Superior was created by the Romans in the third century to administratively separate the south of Britain from Britannia Inferior, the militarised north ('Superior' meaning 'higher' and 'Inferior' meaning 'lower' in the sense of nearer to, and further from, Rome itself).

A century later, this administrative zone was further divided to create Britannia Prima (Wales and the West Country), Flavia Caesariensis, and Maxima Caesariensis. Inis Vectis (later Ynys Weith) would have come under the control of this latter region.

Ceint, whilst perhaps administratively still a part of Maxima Caesariensis in AD 409, seems to have become a petty kingdom by circa 425.

Further north, the marshes around The Wash seemed to have regained the ground they had lost under Roman administration. Second century Roman drainage work, which may have been poorly executed in the first place, was abandoned during the mid-fourth century economic slump and was never repaired.



Maps and text copyright © P L Kessler. An original feature for the History Files.