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Celtic Kingdoms of the British Isles

Celts of Britain



As Roman influence in Britain faded, the various British kingdoms and territories that emerged gradually began to fragment. This was largely thanks to the tradition of dividing territories between offspring, which only served to weaken the entire country. One such fragment of territory seems to have emerged in the mid-fifth century (if not before). This is usually known as Glastenning, a sub-kingdom that probably covered much of the modern county of Somerset, and which lay mostly to the west of the modern town of Glastonbury in the Mendip region of Somerset. There was a Roman settlement at Wells, to the immediate north (possibly with shrines dedicated to the springs there), while the important sub-Roman city of Caer Baddan was a little farther north.

Glastenning (or Glastening) was a sub-kingdom of Dumnonia, and appears to have been subject to its authority for the most part. It may not even have been important enough to be a sub-kingdom, but from the mid-sixth century its immediate rule was under Cyndrwyn Glas, king of Dogfeilion, which itself was a sub-kingdom of Gwynedd. This link was recorded (much later) by William of Malmesbury referencing an early Welsh pedigree that mentioned Glastenning. A son of Cyndrwyn Glas, one Morfael, also became the ruler of the Roman city of Letocetum (Caer Luit Coyt, modern Lichfield) in the eastern half of Pengwern, and his younger brother became king of all of Pengwern, succeeding Cyndrwyn himself.

There is some resistance to linking Glastenning to Glastonbury at all. An alternative suggestion is that the text that links Glastenning to Luit Coyt is corrupt, masking its true nature. Caer Luit Coyt is a location that was certainly linked to the Dogfeilion kings, so this idea cannot be discounted. If it is correct, then the Glastenning of Somerset was nothing of the kind, and would simply have been another region within Dumnonia. However, presuming that Glastenning was indeed Glastonbury, then the Dogfeilion kings had their headquarters at Ynys Witrin, a group of hills and rocky peaks that sit above the marshy and often flooded lands of the Somerset plain. The nearby River Brue offered deep water access to Ynys Witrin which, as well as being a trading port, was also an important site for religious ceremonies.

The name Glastenning would seem to be formed of 'Glast' or 'Glas' with two suffixes added in '-enn' (a form of the more standard Welsh/Brythonic '-ion' or '-on'), and the Saxon '-ing'. By the time William of Malmesbury was writing, Glastenning had long since fallen to the Saxons, so the name had become corrupted. 'Glas' in Welsh means blue, grey, or grey-green, perhaps due to the presence locally of lead or silver mines. Even today, silver coinage in Welsh is 'arian gleision' ('gleision' being the plural of 'glas'). The theory that Glastenning is named after Cyndrwyn Glas is explored further in the entry for circa 550, below. Another possible origin of 'glas' is the Welsh word for glass, 'gwydr', or 'gwydraid' in plural form. The word 'gwydraid' tends to be pronounced in conversation as 'gwydred'. 'Gwydr' is both glass as a material, and a glass drinking receptacle, which in Welsh is 'gwydryn'. Interestingly, the Latin for glass is 'vitrum', with the 'v' pronounced as a 'w'. When mispronounced or corrupted mildly over the course of some generations, this easily gives Witrin, so the Isle of Glass, Ynys Witrin, was the Latin version of the Celtic name. Ynys Witrin, Glastenning, and Glastonbury are all various forms of the same name, and all refer to the same place.

The West Saxons of the mid-seventh century knew Ynys Witrin, the 'Isle of Glass', as Glestingaburg, the 'fortress [or monastic enclosure] of the people of Glas', suggesting that the Britons had a defendable fort there. There does indeed seem to have been a fifth century fort on Glastonbury Tor, which would account for the name Caer Witrin, a variation on Ynys Witrin, with 'caer' meaning 'fort'. The site was also known as Ynys yr Afalon, the Isle of Avalon, 'Avalon' being derived from an old Celtic word for apples, and the site being the place to which the legendary version of 'King' Arthur was taken after the tragic battle of Camlann. Tradition also has it that Joseph of Arimathea visited the site in the first century AD and planted the Glastonbury Thorn, which still flourishes there today despite occasional vandalism.

(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 The Archaeology and History of Glastonbury Abbey, David Ewan Thornton, 1991, 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), and from External Links: Encyclopaedia of Earth, and the Cornwall Archaeology Society.)

fl c.550

Cyndrwyn Glas (the Blue)

King of Dogfeilion & Glastenning.


According to William of Malmesbury, Cyndrwyn Glas settles in Glastenning with his livestock after finding it deserted, migrating there from Luit Coyt (an early connection to this place in Pengwern that will later become important to him and his offspring). His epithet, 'Glas', 'blue', a typical Welsh naming pun for a redhead. Cyndrwyn Glas appears to be a king or sub-king here, and there is also a Cyndrwyn Fawr who appears as king of 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?

In terms of Cyndrwyn's personal name, the first part, 'cyn', is 'dog'. This is a common naming form for Celtic leaders, appearing variously as 'cuno', or 'cune', or 'con'. The second part, 'drwyn', is yet another typically Welsh/Celtic pun which is 'trwyn' in modern Welsh, meaning nose, snout, nozzle, proboscis. In other words, Cyndrwyn means 'dog nose'. When it comes to working out when Glastenning gains its name, it is interesting to theorise that Cyndrwyn himself might not be entirely enamoured with his personal name and may use 'Glas' instead. Once he has taken over the Somerset levels, his people of Glas would be the Glasion, altered here to Glasenn, the origin of Glastenning. There seems to be no sign of Glastenning in any references that would date before the mid-sixth century, so it seems entirely possible (without further evidence) that Glastenning is named after Cyndrwyn Glas.

The Glastonbury region, nominally part of Dumnonia, seems to have experienced a power vacuum in the mid-fifth century which allowed the Dogfeilion to walk in and take over


The name of the last king of Caer Gloui is rather remarkable in that it breaks down as 'Con' meaning 'dog' and 'mail/fael' meaning servant. Speculatively speaking, this 'dog servant' may have links to the kings of Glastenning to their south. Cyndrwyn Glas is also king of Dogfeilion, which means 'servant of [the god] Dagda'.


FeatureOnce the West Seaxe make the breakthrough of defeating Caer Baddan, Caer Ceri, and Caer Gloui, this places the heartland of eastern Dumnonia, and Glastenning itself, under direct threat. However, it seems likely that the three cities have been receiving military support from Glastenning or Dumnonia, and that these latter two kingdoms hold onto the West Wansdyke territory after the three cities have fallen. Incoming Saxon settlers who call themselves the Somersaete are penned in by this barrier.

It may also be possible that an access corridor is maintained along the eastern bank of the Severn which allows the kings of Glastenning to reach the Midlands of Pengwern and further west, to Dogfeilion. While a king of Dogfeilion rules Glastenning in the middle of this century, it seems a subsidiary branch from Pengwern has gained it by the early seventh century.

Glast ap Cyndrwyn?

Extrapolated from the name of his son, Morfael.

c.610s - 620s

FeatureIt is around this time that the Britons of Glastenning found Glastonbury Abbey, which remains one of Britain's best known abbeys until its closure at the Dissolution. 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.


While Glastenning is inherited by Morfael, this point marks the first appearance of the Dogfeilion in Powys and Pengwern. Morfael is also a sub-king in Pengwern, at Caer Luit Coyt, while his brother, Eiludd Powys, becomes king of Powys (which incorporates the Pengwern territory). Given Welsh emphasis on ancestry to qualify for a throne, it seems likely that a Dogfeilion leader (probably Cyndrwyn Glas) has married a daughter of the king of Powys, qualifying his descendants to rule Powys by the rules of descent of Gwynedd (which had been inherited from their ancestors, the Venicones). Romans and Romano-British use primogeniture, but the Pictish rules are that any descendant, regardless of the form of that descent, is qualified to inherit (meaning that even bastard sons of wayward daughters can show up and claim a piece of a territory or even kingship). The fact that the Dogfeilion are accepted as rulers of Powys (as well as that part of Powys that is known as Pengwern) is very telling. There has to be a valid claim of descent.

fl c.612

Morfael ap Glast

King of Caer Luit Coyt & Glastenning.

fl c.645

Morgan Glas (the Blue)

King of Glastenning.

652 - 658

Two West Seaxe victories in 652 and 658 see them occupy the entire Glastonbury region, and the British sub-kingdom of Glastenning ceases to exist. Its overlord, Dumnonia, also suffers extensive loss of territory in the remaining parts of Somerset and in Dorset. Glastenning is rendered as 'Glestingaburg' by the local Saxon Somersaete ('the somer settlers'), but the the abbey that has recently been founded there survives and prospers, and initially does so under British abbots. The Dogfelion kings also lose Pengwern in 656, and already seem to have lost control of Pengwern's master, Powys, so now they are cut back to their ancestral territory of Dogfeilion.