The Irish Migrations That Transformed Britain in the Dark Ages

The Dark Ages in the British Isles were a period of considerable movement. Many people are aware of the Anglo-Saxon migration to Britain, however, the Irish moved as well.

Mar 22, 2024By Caleb Howells, BA Doctrines and Methodology of Education

dark ages irish migrations



  • Irish migrations during the Dark Ages significantly impacted Britain, with settlers influencing Cornwall and Wales through cultural integration and the introduction of the Ogham script, evidenced by numerous inscriptions.
  • Conflict arose as native leaders like Cunedda Wledig opposed the Irish settlers, driving them from regions in Wales and shaping the early medieval political landscape of the British Isles.
  • The establishment of the Irish kingdom of Dal Riada in Scotland and the friendly Irish kingdom of Brycheiniog highlight the complex interplay of migration, warfare, and alliance during this period.


During the Roman era, Britain experienced a measure of tranquility. Even though there were usurpations and break-away empires at times, the Britons themselves had a relatively stable existence on their island. However, after the Romans left in 409, the Dark Ages began, opening the door to considerable change in Britain. It is widely known that the Anglo-Saxons began migrating en masse to Britain in the fifth century, an event that eventually led to modern England. It is much less well-known that the Dark Ages were also marked by Irish migrations to Britain.


Irish Migrations Before the Dark Ages

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Depiction of a raid by Irish warriors from The Image of Irelande, by John Derrick, 1581, via Wikimedia Commons


Given the fact that Ireland is just next to Britain, it is remarkable that Irish tribes did not begin invading Britain earlier than they did. Perhaps they were intimidated by the power of the Roman legions on the island. In any case, the historical record indicates that the first major Irish incursion into Britain occurred in the 360s. Apparently, for quite a large portion of this decade, Roman Britain was being attacked by tribes from outside the empire, such as the Picts and the Scots. The Picts were the Brythonic tribes from the north of Britain, essentially from what is now Scotland. On the other hand, the Scots were among the tribes from Ireland.


By the year 367, these barbarian tribes had overwhelmed Roman Britain. They had killed Nectaridus, the Count of the Saxon Shore, and captured Fullofaudes, the Dux Britanniarum. It was a dire situation for the Romans, but they were able to respond effectively. Theodosius I (before he was emperor) was one of the main commanders sent to deal with the situation.


birdoswald roman fort illustration
Illustration of Birdoswald Roman Fort on Hadrian’s Wall after the Roman administration collapsed, Philip Corke, via English Heritage

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Although the Romans were able to stop the invaders and re-establish control over most of Britain, it is likely that not all the invaders actually returned to their homeland. It may well be the case that many of them settled in the furthest corners of Britain, where the Roman presence was most limited. For example, some of them may have settled in Cornwall and Devon, or parts of Wales.


The power of the Romans over these parts of Britain had weakened a lot by this point. Due to this, it is possible that the Romans even turned a blind eye to independent kings cropping up in communities of these barbarian tribes. Medieval texts claim that Irish tribes settled in some of these areas in the late fourth century, before the complete end of Roman rule in Britain. The family of a king named Eochu Liathán are said to have established colonies in Wales and Cornwall in this period.


Migrations in the Dark Ages

ogham stone ardmore
An Ogham Stone found at Ardmore, via the Digital Journal of Irish Studies


Whether or not any Irish tribes did settle parts of Britain before the Dark Ages began, they certainly did afterwards. By the year 409, the Roman legions had been withdrawn from Britain and the Roman administration had been expelled by the natives. The following several centuries are known as the Dark Ages of Britain. We know for sure that parts of Cornwall and Wales were extensively inhabited by Irish settlers because of the inscriptions which have been found there.


Almost 400 inscriptions have been found on memorial stones of various types in Wales and Cornwall which are written in a script called Ogham. This script was used by the Irish to write their language. These inscriptions often appear together with a Latin inscription saying the same thing. The earliest of these date back to the fifth century, which ties in with the idea that the Irish began settling the area in that century or slightly earlier.


Opposition by Cunedda Wledig

cunedda morgan history kings britain dark ages
Illustration of Cunedda and Morgan from Peniarth MS 23, fifteenth century, via Wikimedia Commons


One of the most notable events in fifth-century Britain, according to the available evidence from medieval texts, was the war between the Irish living in Wales and a warlord known as Cunedda Wledig. According to the ninth-century Historia Brittonum, the family of Eochu Liathán settled in the southern region of Wales until they were driven out by Cunedda and his sons. Later on, this same record refers to Cunedda and his sons driving the Irish out of the region which subsequently became the kingdom of Gwynedd, which was the northwest corner of Wales.


Cunedda’s many sons were said to have founded kingdoms in the regions that they conquered. These kingdoms covered the entire northwest portion of Wales, indicating the extent of the Irish settlement before that time. However, it is notable that none of Cunedda’s sons founded kingdoms as far south as Dyfed, the region in the southwest corner. This is evidence against the claim in the Historia Brittonum that Cunedda drove out the Irish from that portion of Britain. Everything else indicates that Cunedda’s conquests of the Irish did not go further south than the northern border of Dyfed.


The Expulsion of the Irish from Dyfed

stained glass dark age king tewdrig
Stained glass window depiction of King Tewdrig, Llandaff Cathedral, Glamorgan, via Wikimedia Commons


Nonetheless, the Irish rulers were driven out of Dyfed eventually. Medieval king lists from the Dark Ages show that the Irish ruled that region for over a century until about the year 500. After a series of Irish names, the king lists reveal a sudden change — two names appear which are decidedly Roman: Triphun (from Tribunus) and Aircol (from Agricola). In other versions of this list, Triphun is made a descendant of Magnus Maximus, the Roman Emperor who ruled over Britain in the fourth century.  Evidently, the dynasty of Irish kings was driven out in about the year 500 and replaced by King Triphun. The lists which do not mention the Irish names are straightforward genealogies. On the other hand, the lists which do contain the Irish names simply present the kings of the region, without regard for their descent.


As to who was responsible for driving out this Irish dynasty, it could have simply been Triphun. However, on the basis of other records, some scholars have suggested that it was King Tewdrig, the ruler of the southeast portion of Wales in the fifth century. He would then have appointed Triphun in place of the Irish rulers.


The Dark Age Irish Kingdom of Brycheiniog

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A view of Brecon Beacons National Park, named after King Brychan, photo by Adam Burton, via National Geographic


King Tewdrig had a friendlier relationship with a different Irish king. In a text called De Situ Brecheniauc, Tewdrig is said to have sent his daughter to Ireland. There, she married an Irish king named Anlach. The couple returned to Britain after they bore a son, whose name was Brychan. Anlach ruled over a portion of Britain just north of Tewdrig’s kingdom, evidently as a friendly king. However, Anlach did wage war against a king named Banadl, the ruler of a neighbouring kingdom called Powys. After Anlach died, his son Brychan succeeded him. The region then became known as Brycheiniog. Therefore, Brycheiniog was a kingdom that had a partial Irish origin. The Dark Ages were full of political marriages between kingdoms, so this is not surprising or out of the ordinary.


reconstruction dark ages village
Reconstruction of a Dark Age village, via the Ancient Technology Centre, Dorset


The medieval texts do not say whether or not Brychan had an inheritance in Ireland itself. Even if he did rule over some portion of Ireland, there is little evidence of any continued cultural connection between Ireland and Brycheiniog over the centuries.


Dal Riada

Dunadd hill fort, possible capital of Dal Riada, via Britannica


The Dark Ages also saw the emergence of an Irish kingdom much further north. This kingdom was known as Dal Riada. Unlike some of the other Irish kingdoms established in Britain in the Dark Ages, this was not completely cut off from Ireland itself. Dal Riada encompassed the northern part of what is now County Antrim, in the northeast corner of Ireland. But most of the kingdom was in what is now Scotland. At its height, it covered a large portion of Scotland’s western coast.


According to legendary Irish texts, Dal Riada was founded in the early Dark Ages by a king named Fergus Mor, about the year 500. However, an older legend, recorded by the eighth-century historian Bede, attributes the founding of Dal Riada to a certain “Reuda.” Given the lack of contemporary evidence, it is impossible to say for sure how it was really founded, or when. Some scholars even argue that it had been culturally Irish for centuries before the Dark Ages.


The Irish Migrations of the Dark Ages

soldiers ireland albrecht durer
Thus go the soldiers in Ireland, beyond England. Thus go peasants in Ireland, by Albrecht Durer, 1521, via Irish Archaeology


In this article, we have seen that the Dark Ages were a time of considerable movement for the Irish tribes. In fact, even before the Dark Ages began, some of the Irish were settling in Britain, just outside the reach of the Romans. These migrations evidently increased significantly after the Romans left Britain and the Dark Ages began. They occupied enormous portions of Wales. Although most of them were driven out by Cunedda and his sons, the Irish dynasty ruling over Dyfed still remained. It was only in about the year 500 that the dynasty in Dyfed was expelled, with King Tewdrig possibly being responsible for that.  One of Tewdrig’s daughters married an Irish king, leading to the foundation of a friendly Irish kingdom just next to Tewdrig’s domain. Furthermore, at about the same time, Fergus Mor supposedly led a migration from Ireland to Scotland, establishing the kingdom of Dal Riada.



What was the impact of the Irish migrations on the culture and language of Wales and Scotland?

The Irish migrations significantly influenced the culture and language of Wales and Scotland, introducing Gaelic elements that blended with the local Celtic traditions. This fusion enriched the linguistic landscape, leading to the development of distinct Gaelic dialects in Scotland and contributing to the cultural tapestry of Wales, where Irish heritage became intertwined with Welsh traditions.


Why did the Irish migrate to Britain during the Dark Ages?

During the Dark Ages, the Irish migrated to Britain primarily due to political instability, economic hardships, and the allure of new lands for settlement. These migrations were part of larger movements of Celtic peoples, driven by the societal upheavals and the expansionary ambitions of Irish kingdoms.


What happened to the Irish communities in Wales and Cornwall after the Dark Ages?

After the Dark Ages, the Irish communities in Wales and Cornwall experienced assimilation into the local cultures, with their distinct identities gradually blending into the broader Celtic societies. In Wales, the Irish influence persisted in local customs and linguistic traces, while in Cornwall, the assimilation led to a more integrated community, with Irish heritage becoming a part of the Cornish cultural mosaic.

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By Caleb HowellsBA Doctrines and Methodology of EducationCaleb is a published history author with a strong interest in ancient Britain and the Mediterranean world. He holds a BA in the Doctrines and Methodology of Education from USILACS. He is the author of "King Arthur: The Man Who Conquered Europe" and "The Trojan Kings of Britain: Myth or History?". Caleb enjoys learning about history in general, but he especially loves investigating myths and legends and seeing how they might be explained by historical events and individuals.