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The Kingdom of Dumnonia: Modern Day Southwest England

I enjoy researching and writing about British and royal history. Most people have not heard of the Kingdom of Dumnonia. Welcome.

The Celtic tribes resident in southern England before and during the Roman era. The Dumnonii tribe populated the Kingdom of Dumnonia.

The Celtic tribes resident in southern England before and during the Roman era. The Dumnonii tribe populated the Kingdom of Dumnonia.

Where Was the Kingdom of Dumnonia?

The Kingdom of Dumnonia existed in southwest England between the 4th and 8th centuries. It encompassed what we know today as Devon, Cornwall and parts of Somerset and Dorset.

The kingdom was populated by the Dumnonii (sometimes called Dumnones) tribe. They were feisty people with Bronze Age Celtic origins, and when the Romans arrived in the area, they found that the Dumnonians were unwilling to submit to their dominance. It seems that a deal was struck that afforded the Dumnonii a generous degree of self-government in return for cooperation with the new arrivals.

The Romans made the capital for the kingdom Isca Dumnoniorum meaning "Water of the Dumnonii." This is the modern-day city of Exeter. It later moved west to Tintagel. Tintagel Castle was a primary domain of the legendary ruler King Arthur and his court, including Merlin, the sorcerer.

Dumnonia or Damnonia?

There isn't a definitive list of Dumnonian kings but references in texts written by later luminary Geoffrey of Monmouth and the 6th-century monk and scribe Gildas suggested who ruled. The intriguingly named Petroc Baladrddellt ap Clemen, Petroc the Splintered Spear, son of Clemen, and Geraint Llyngesic ab Erbin or Geraint the Fleet Owner, son of Erbin, were among them.

The Strathclyde area of Scotland was home to the Damnonii tribe, which was the name sometimes attributed to the residents of Dumnonia hundreds of miles to the south. The accepted spelling is Dumnonia for the English kingdom.

The confusion was due to Gildas (later St. Gildas), who used his writing to discredit King Constantine of Dumnonia and his predecessors by making a comparison between the kingdom and damnation. The rulers were presented as biblical beasts, and Constantine was referred to as the "tyrannical whelp of the unclean lioness of Damnonia" (Dumnonia).

The Kingdom of Dumnonia, Anglo-Saxon West Wales

The correct etymology for Dumnonia is less judgmental. The Celtic words dubno and dumno meant "world" and "the deep." At the far west of the Dumnonian peninsula, the Cornovii tribe settled, and this is where the name "Cornwall" originated.

The Anglo-Saxons referred to Dumnonia as West Wales. This was additional to the Wales that we recognise today. Both areas contained Celts who spoke in Brythonic dialects.

The old English word for "foreigner" was waalsch from the Dutch language. To the Romans and Anglo-Saxons, the Celts were different, and their customs were foreign.

St. Michael's Mount in Cornwall (Ictis) is linked to the mainland by a causeway which is passable when the tide is out.

St. Michael's Mount in Cornwall (Ictis) is linked to the mainland by a causeway which is passable when the tide is out.

Life in Dumnonia and St. Piran's Importance

The people of Dumnonia survived by hunting, fishing, mining tin and copper, farming and agriculture. Tin mining had been conducted since pre-Roman times, and it flourished during the Roman era when trade links to other parts of the Roman Empire were formed. St. Michael's Mount acted as the port for trade; back then it was called Ictis.

The faith turned progressively towards Christianity as the Romans influenced the population of the kingdom. The most famous Cornish saint was St. Piran, an abbot who lived in the 5th century.

He became the patron saint of tin miners with the saint's day of 5th March, and numerous place names have his name as their inspiration (e.g., Perranporth). Perran is the Cornish language version of Piran. St. Piran's Cross at Perranzabuloe is the oldest stone cross in the southwest.

St. Piran's Cross in Perranzabuloe.

St. Piran's Cross in Perranzabuloe.

Dumnonia Becomes Cornubia, West of the River Tamar

Battles fought between Anglo-Saxon and Dumnonian armies resulted in Wessex's expansion into and annexation of Dumnonian territory. The campaigns of King Egbert of Wessex in the early 9th century sealed the kingdom's fate.

The Anglo-Saxons controlled modern-day Somerset, Dorset and Devon. The much smaller Dumnonia became Cornubia and later Cornwall. Devon, as a place name, evolved from Dumnon into Defnon and then Devon.

A rebellion in 838 failed to restore land to the Celts, and Donyarth, the last King of Dumnonia, died in 875.

In 936 King Aethelstan of England set the border between Cornwall and Devon along the north-south route of the River Tamar where it remains. The Cornish-speaking people call their country Kernow, and the Tamar Suspension Bridge over the river between Saltash in Cornwall and Plymouth in Devon is seen by independence campaigners as a defining point between the two nations. The indomitable Dumnonian spirit lives on.


This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2022 Joanne Hayle