

The Irish settlements and raids on the Cornish coast of the Severn Sea depopulated the area of its inhabitants. The eastern Anglo-Saxons could not have been the cause of the Breton migration, but the western Irish were. Yet the Roman Armoricans had begun allying with and giving land to immigrant Bretons in 409 AD, to bolster their numbers against a continental Saxon scare. The Armorican migration was occurring in the 4th, 5th, and 6th centuries, but Saxon power hadn't reached Wales until the after the Battle of Mount Badon c. The traditional narrative of Saxon invaders forcing the Britons of the Welsh Marches across the sea can't be true. Linguistic and historical evidence shows that most of the Britons who fled to Brittany originated in Devon, contrary to Gildas' accounts of Central and Eastern Wales. The Severn Sea (modern Bristol Channel) was the stage for major Irish settlement into Devon. The threat of an Adventus Scottorum kept the western kings awake at night. The territories of Devon and Lancashire were strongholds against the encroaching Irish powers, stopping the Gael from traveling further inland or northward. In this instances it was merely a temporary occupation of the upper classes by nobles funded by Irish kings.

But make no mistake, the Irish in the end left no major genetic impression on the Welsh population. A Welsh poet might call another poet's work "diseisnig" and "diwyddelig", that is, untainted by English or Irish. Another is Dolwyddelan (Dole-with-eh-lahn), which derives from Gwyddelan and Gwyddel, which is a Welsh term for a Gael or Goidel. Many place names in Wales to this day derive from Irish or reference Ireland, such as Llyn Iwerddon, "Lake of Ireland", in Caernarvonshire. Many ogham stones from this area (the most in all of Britain) are written in Gaelic, not Brythonic. Many places such as Dyfed or Lleyn were bilingual with Gaelic, at least among the nobility. The ruling dynasty of Dyfed came from Leinster. How extensive were these raids? They were settlements. Dyfed), Cornwall (Dumnonnia), and Argyll (Dál Riata). The most Irish-afflicted areas of Britain were the south west of Wales (Pembrokeshire, a.k.a. The five kingdoms of Ireland (cóiceda) were fighting amongst themselves, but like the Norwegians centuries later, internal conflict never deterred expansion.
