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Dumnonia was a large Celtic kingdom that encompassed all of Cornwall (Cornubia), Devon (Dyfneint), and much of Somerset (the 'Summer Land' of the Mabinogion). Although it had emerged prior to the period of study on wikitree it seems to be a series of small tribal groups and the "kingdom" didn't emerge until c the 4th Century. The Kingdom is named after the Dumnonii, a British Celtic tribe that was living in the district at the time of the 2nd Roman invasion and is noticed in Ptolemy's Geography.

Its major centre was at Isca Dumnoniorum, now modern Exeter. The Celtic name would have been Isca (meaning 'city of water'), late British period would have been Caer Uisc (Fort on the Water).

During the Roman period there seems to have been a compromise reached between the Dumnonii and the Roman occupation. Rome needed the benefit of the tin mines but was not willing to commit resources to maintaining security in the region. Thus the Dumnonii maintain a semi independent posture. The region appears as a Kingdom in the time of Magnus Maximus around 383, before he departs for Rome.

Notable Rulers

c.290 - c. 305. Caradoc / Caratacus / Caradocus. Appears as "Duke of Cornwall". He is trusted advisor of Eudaf Hen of Ewyas. Around this time the hill fort complex of Cadbury-Congresbury, (close to Yatton in North Somerset), is built and occupied. Excavations suggest continuous occupation between the late 3rd and the sixth century. There is also evidence at Ipplepen, Devon of continuous occupation with an archeology project excavtion of a Roman cometary showing that the cemetery was in use for three hundred and fifty years after the end of direct Roman administration of Britain.

c. 300. Mauric / Meurig. Appears in source. He was the first son of Caradoc but predeceases him.

c.305 - 340. Donaut / Dionotus / Dynod. Brother to Caradoc. Appears as "Duke of Cornwall". He will leave the region to his son-in-law, Conan.

c.340 - c.387. Conan Meriadoc / Conanus. It is not clear in source whether these are the same person as above. He appears as King of Vannetais and Duke of Cornwall. He will leave Dumnonia to his eldest son by a lady named Ursula. In 383, Magnus Maximus, military commander in Britain, leaves for his attempt to gain the Roman Empire. He takes Conan with him. He establishes Conan Meriadoc as king in Armorica (now Brittany) at the start of his campaign. Sources suggest that Conan is the nephew of Octavius, Maximus' predecessor. The relationship could make Octavius the father of Maximus' wife, as Conan is also her cousin. Conan's son, Gadeon, is mentioned in the Dream of Macsen Wledig (as is his brother, Adeon).

c.387 - c.390. Gadeon / Cadfan / Adeon. He is either, depending on the source followed, a son or brother to Conan Meriadoc. The weight of evidence suggests son. His half brother, Erbin, ruled Vannetais.

c.390 - c.400. Guoremor / Gwrfawr / Vorimorus ap Gadeon. He was a son of Gadeon. He is generally recognised as the first independent king of Dumnonia. At around this time, archaeological evidence suggests that Isca was abandoned and the main centre was moved to Tintagel. The lands of Dumnonia were increased and the border moved east. The Kingdom flourished during this period and evidence suggests Tintagel a significant centre. The people here are clearly well-off, and maintained trading links with the Mediterranean and established new ones with the Franks via traditional markets in Gaul.

c.400 - c.410. Tutwal / Tudwal ap Guoremor. He was a son of Guoremor. He is suggested to have married Gratianna, the youngest daughter of Magnus Maximus. This is supported by the naming of his eldest son, Magnus.

c.410 - c. 435. Marcus Conomari / Conomor / Cynfawr ap Tutwal. He was the eldest son of Tutwal. Marcus Conomari (or Cunomorus) is apparently the name inscribed on stone and later found between Castledore and Fowey in Cornwall. The inscription is not complete but the likeliest translation, of the Latin inscription, is Here lies Drustan, son of Cunomori. Legend ties Drustan with Tristan, of Lyonesse (the Arthurian Legend) Tristan & Iseult, which relates events during the reign of Cyn-March ap Meirchion of Cornubia. In the work called Life of St Pol de Leon, completed in 883, the king is referred to as King Marc whose other name is Quonomorus, or Cunomorus, meaning hound of the sea.

c.435 - 443. Constantine Corneu (of Cornwall). He was a son of Marcus Conomari. He appears to have divided the Kingdom between two sons. Erbin and Merchion.

443 - c.480. Urban / Erbin ab Custennyn. Sometimes as Erbin ap Constantine. He was the son of Constantine of Cornwall. He abdicated in favour of Gerren, his first son, before 480. Cornubia (Cornwall) is governed as a sub-kingdom by Erbin's younger brother, Merchion. Upon his death, the region is further sub-divided to create an independent Lyonesse (modern; Isles of Scilly).

c.480 - 508. Gerren / Gerontius / Gereint Llyngesog ab Erbin. He was the first son of Erbin. He plays a significant part in the Arthurian Legend and features in the Arthurian story of Culhwch and Olwen. He is probably the brother of Veneva (the Romano-British form of Guinevere), who marries Arthur. In the legends associated with the Saxon invasion of this part of Britain Cerdic and his (young) son Cynric, together with Saxon and possibly some Jutish companions, land in five ships on the south coast of Britain at Cerdices ora. This is c. 495 depending on source. In 501, a newly arrived Saxon chieftain and his two ships of followers kill a Briton of very high rank at Portesmutha (modern Portsmouth). Although the Briton killed may have been of the kingdom of Rhegin it is possible the Briton could also be Gereint of Dumnonia.

c. 500. Dywel ab Erbin. Not named as ruler but appears in the same Arthurian legend and is said to have served with Arthur. Said to have died c.520. His soon may have been St Pirran.

c.508 - c.530. Cado / Cato / Cadwy ab Gerren. Son of Gerren. He was King of Dumnonia & Duke of Cornubia. The line of the second son of Merchion ab Constatine seems to have died out and the titles are joined again. Cado, this person, Cado, is presumed to be Duke Cador of Cornwall of Geoffrey of Monmouth's work. It is probably this Cado who is mentioned in connection with Arthur in the Life of St Crannog (of Ceredigion). Cado appears to have had two brothers, Iestyn / St Justin and Selyfan / Solomanus / St Selevan and a sister St Breage.

c.530 - c.560. Custennin ab Cado / St Constantine. He was King of Dumnonia and then High King of Britain until c 540. He is one of the kings attacked by Gildas, On the Ruin of Britain, and is referred to as a 'tyrant whelp of the filthy lioness of Dumnonia'. After 540 he retires to a monastry and was killed in 589.

c.560 - 598. Gerren rac Dehau ('for the South'). He was a son of Constantine. He is noted as the Briton that fought against the Bernician Angles at Catreath.

598 - 613. Blederic / Bledric ap Custennin. A brother to Gerren and son to Constantine. Killed at Battle of Bangor-is-Coed (Bangor on Dee) by Aethelfrith. Following significant defeats by the Saxons the British regimes collapse. The historical record for this period becomes sketchy. Bledric seems to have been followed bu his son.

613 - c. 620. Clement ap Bledric. Son to Bledric. Saxons have now penetrated deep into Dumnonia. Badly defeated at the Battle of Beandun (probably Bindon, immediately east of Axmouth in Devon), Clemen, is forced to retreat back to Caer Uisc (Exeter). Independent groups of Saxons are able to make inroads, forming the Dornsaete (Dorset settlers) and Somersaete (Somerset settlrs).

c. 630. Petroc Baladrddellt (Splintered Spear) ap Clemen. He is the son of Clement. Noticed as King in source. Cenwalh of the West Saexe makes a breakthrough against the Dumnonian defensive lines at the battle of Bradford-upon-Avon. The Dornsaete who have been slowly pushing against the Dumnonian borders now come under West Seaxe (West Saxon) control whilst Dumnonia loses more territory to the invaders.

c. 660. Culmin / Cwlfyn ap Petroc. He is a son of Petroc. He is defeated at the Battle of Peonna (Penselwood, Somerset). Glastonbury Abbey comes under the control of the West Saexe although retains its British abbot.

c.680. Dungarth ap Culmin. A son to Culmin. All of Somerset now fall and attacks are made on Devon.

bef 700 - 710. Gerontius / Gerren ap Dungarth. His is a son of Dungarth and appears on record as King of the Welsh (non-Saxon speaker). Defeated by Ine of Wessex and killed. Dumnonia now appears to be restricted to, roughly the modern border of Cornwall.

c.710 - c.715. Ithel ap Dungarth ('the Rock'). He was a brother to Gerren and son to Dungarth. Sources suggest, but are not sure, that he ruled.

From this point, as Dumnonia is crushed by Wessex, the line of Kings can be said to have ceased. Ithel's immediate successor is not known, unless it his son who is thought to be active in the 730s. Even this son, Dyfnwal, cannot be confirmed as king. His name, and that of his successors, is mentioned only in the Book of Baglan, a collection of Welsh manuscripts compiled in 1600-1607 and unreliable as source. In 722 the Annales Cambriae refers to three great battles. These were presumably fought between Cornwall (south British in source) and Wessex. The battles take place at Hehil, Garth Maelog, and Pencon (Pencoed). The Britons won all three battles and they are important as, it seems, that Wessex, now caught up in its own conflicts with Mercia, withdrew. These actions resulted in, roughly, 100 years of peace for the region.

wikipedia maintains a List of Rulers of Dumnonia


The early history of Dumnonia appears in a variety of sources but is difficult to reconcile with historical fact, legend and pseudo-history appearing in source. The main sources available include Gildas's De Excidio Britanniae and Nennius's Historia Brittonum, the Annales Cambriae, Anglo-Saxon Chronicle, William of Malmesbury's Gesta Regum Anglorum and De Antiquitate Glastoniensis Ecclesiae, along with texts from the Black Book of Carmarthen and the Red Book of Hergest, and Bede's Historia ecclesiastica gentis Anglorum as well as "The Descent of the Men of the North" (Bonedd Gwŷr y Gogledd, in Peniarth MS 45 and elsewhere) and the Book of Baglan. It generally requires input from multiple sources to discover the truth to support early profiles.

Dumnonia on wikipedia

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