The one question left answered in this theory is: Who was Arthur? Is it possible to identify one single person as Arthur; or is Arthur an epithet given to a number of kings, perhaps to any Dux Bellorum of the Britons?
Summary
I have attempted to show in King Arthur and Drumchapel that both Arthur and Merlin were based in the area. My analysis of Arthur's battles has also pointed to a Scottish base. That would be consistent with a British king fighting off Picts and Angles in the sixth century.
The battle of Bassas, I have suggested is around 508 AD; probably an internal battle of King Arthur's to establish his power base in the region over other rivals for his kingship. Although Nennius places this battle as his sixth, it may therefore have been earlier. The battle of Badon Hill is about 516 AD, and logically most, if not all of Nennius' battles must been in that timeframe. The battle of Camlann in 539 AD would have been Arthur's final battle after 20 years of peace in the region. So then, if Arthur was a real king, then we have an approximate reign length for him: 508 - 539 AD.
One explanation of the final battle being twenty years after Badon would be the natural disaster of 535 AD, either a volcanic explosion or a comet, creating a worldwide environmental aftermath which lasted several years. This failure of crops, the drop in temperature and the onset of the Black Death would have created unrest and probable resentment of the High King, whose rulings may have been ineffectual against the global disaster. In The Celts of the West Veneslas Kruta explains that "the ideal sovereign... was supposed to ensure a perfect climate, a temperature and rainfall favourable to vegetation, an abundance of livestock and good harvests, an absence of vermin and disease, peace and respect for the law." We can then surmise that Camlann was a battle between those still loyal to Arthur - most probably only his veteran warriors - and a younger generation who blamed him for the desolation of the time.
Theory
The King of the Britons at this time is Clinoch; based at Ail Cluathe (Dumbarton). The reign dates of Arthur almost exactly correspond to that of Clinoch. So then is Clinoch the real Arthur? Unfortunately we know little of this Strathclyde king. He had a brother Cinbelin and his father was Domangall Hen, the previous king of Strathclyde. Arthur is legend is said to be related to Cymbeline; is Cymbeline (Cinbelin) then Arthur's brother? Evidence is scant but there are compelling similarities.
Arthur was supposedly a High King of the Britons. I will attempt to show that Clinoch was also the High King of the Britons. Since there can be only one High King at any time, this must mean that Clinoch was the real Arthur.
Validation
To validate this theory, I will use a method similar to mathemathical induction. First I prove the first case, then assume for the general case and prove for subsequent cases.
First case
Domangall - Domnagart
It is necessary then to look at other king lists to see if any kings match. Domangall Hen, Clinoch's father was King of Strathclyde before him. His reign length almost exactly matches that of Domangart of Dalriada. The similarity of the names Domangall and Domnagart and reign length strongly suggest the same person; a High King of both Strathclyde and Dalriada. The gall ending of the Strathclyde king also points to Gaelic (Dalriadan) influence.
In the Annals of Ulster calls Domnagart Domhangart macnisse reti secessit. Marjorie Anderson's Kings and Kingship in early Scotland takes this to be an epithet son of Ness, a possible divinity but notes that elsewhere in other annals "it is an epithet of Fergus, Domangart's father. The death of a bishop of Connor called MacNisse is entered in AU [Annals of Ulster] immediately after that of Domangart, in T [Annals of Tigernach] four years (eight lines) further on, so perhaps there has been confusion somewhere."
One reason for this is the annals were primarily religious texts written by monks. Down was the parish founded by St. Patrick and the first bishop was called Fergus. Connor was the adjacent see to the north of Down and founded by St. Macnisse in 480.
This brings the conclusion that Fergus of Dalriada was also known as Ness, and probably was the first bishop of Down after St. Patrick's death. The expansion into Dalriada was probably then a religious one bringing back christianity to the west of Scotland.
His son Domnagart founder of the parish of Connor succeeded him as king. Indeed at the end of his reign Domnagart probably went back to religion. Marjorie Anderson again... "There seems to be a tradition that Domnagart died in religon. AI [Annals of Ireland] enters the quies (the usual word for the death of a churchman) of Domangart of Kintyre. AU [Annals of Ulster]'s secessit may therefore be translated 'withdrew (from the kingship, or into religion). The phrase of Kintrye may possibly have reference to his life in religion. His grandson Aedan also seems to have ended his life in a monastery."
This explains the death of the Bishop of Connor marked as four years later in the Annals of Ulster; Domnagart died, after giving up the kingship and returning to religion in Kintyre, around the year 510 AD. As he had previously founded the see of Connor in 480 AD, this explains the Hen part of Domangall Hen, as he would have been elderly when assuming the throne.
As we shall see this withdrawing from the kingship is a pattern not just limited to Domnagart and Aedan.
General case
I would suggest that these kings are one and the same person and that Domangall was indeed the Ard Righ (High King) of the region based at Ail Cluathe. Given this then what does this tell us of Clinoch?
Subsequent cases
Clinoch - Constantine - Comgall
Given this the facts fall into place. At the time of the early to mid sixth century, the king of Strathclyde was the high king of the region, based in Ail Cluathe. Domangart of Dalriada had two sons: Comgall and Gabran, both becoming Kings of Dalriada.
Hence Clinoch then must have been Comgall, King of Dalriada. Gall can mean stranger in Gaelic, showing that indeed Clinoch was British and not Gaelic. The reign length in the Annals of Comgall and Clinoch almost exactly correspond, again to prove the point.
Also, Gildas talks of Constantine of Damnonia. This is Gildas latinising the root of Com[gall] and obtaining the romanised Constantine. The regnal lists mention Congal or Congel not Comgall. Marjorie Anderson's terminology of regnal lists in Kings and kingship in early Scotland shows list K being almost exactly the same as the other lists, except that a king known as Constan fitz Doengerd with the same reign-length as Congal [Comgall] entered directly after Congal. All other reign-lengths match the other kings. Marjorie Anderson notes: 'K, in which latin parts of the list are translated into fourteenth century French, is embedded in the Scalacronia of Thomas Gray, a Northumbrian gentleman who began to write his chronicle in 1355 when he was a prisoner in Edinburgh, and who died in 1369.' It seems then that Gray must have interpreted a footnote mentioning Comgall's romanised name and pedigree as another king, not seen in all the other texts.
Thus, again Comgall must be King of Strathclyde (Damnonia being another name for the region). Gildas mentions Constantine as a "whelp"; in Gaelic this epithet becomes culen, thus the British clinoch. Clinoch is the Arthur referred to by Nennius.
Cinbelin - Modred - Gabran
Gabran was connected to King Brychan by marriage to his daughter Luan. He probably moved to the Manaan region and was henceforth connected with the Picts.
Gabran later divorced Luan to marry Ingenach, daughter of Domangall Hen. Since we have shown that Domangall and Domangart are one and the same, this means that Gabran married his own sister; hence the Arthurian legend of Arthur and Morgan. In the context of the times, with many people dying from famine and plague, this becomes more understandable.
In the Annals, Comgall was to lose the kingship to his brother, Gabran around 540 AD. The Annals of Tigernach record the date as 537 AD. Whatever the date, it fits for the battle of Camlann. Gabran is suggested to have been a sub-king of Manaan and thus validates the siting of the battle in Stirlingshire. The Annals Cambriae record the battle in 539 AD, mentioning that Arthur and Medraut perished. (Medraut is identified as Modred, a Pictish prince; hence the legend that Arthur died in battle against the Picts.)
Comgall was overthrown and was probably banished from the kingdom. The Annals of Ulster give his reign ending around 538 but his death at 542 or 545 AD. Indeed, Gildas in his De Excidio Britanniae states: "the despot Constantine, whelp of the filthy lioness of Damnonia... I know full well that you are alive..." confirms that Comgall (Constantine) was banished. Gildas also refers to Constantine as a bear, which is a frequent epithet given to Arthur. (See also the entry for the Galbraith family.)
Ending of the High Kingship
Equally the Arthur legend of being defeated by his nephew is seen when Gabran is defeated by Conall in 558. The mention that Arthur and Modred perished could be taken to mean that with this battle the concept of High Kingship (Ard Righ) died - and thus Arthur perished. Gabran may have been the last Ard Righ; and the kingdoms of Strathclyde and Dalriada would have resumed their own kingships, although with closer ties than before. Marjorie Anderson in her Kings and kingship in early Scotland notes that 'In T [the Annals of Tigernach], Domangart, Comgall and Gabran are identified as "king of Alba", Conall son of Comgall as "king of DalRiata" '.
Later kingships reinforce the Arthurian legend
The political situation at the time explains why Aedan married a British wife - to increase his chances to the throne, and to try and reinstate the Ard Righ- and why he called one of his sons Artur, which would have been a strange proclamation of destiny for the young prince. (Similarly another son Conaing was named after the English word for king.) That Artur was to die in battle would have only increased the legend. Time would pass and the High Kingship as a concept would die also leaving only the legend of Arthur, the high kingship, remaining.
What then of the Arthurian legends? These can be put into context when it is realised that Arthur is just an epithet meaning High King. The Welsh form of Ard Righ gives Arth Ru and in derivation gives Arthur. Thus Arthur obtained legends that not only corresponded to Clinoch (Comgall) but to other High Kings and later Kings of Strathclyde. This would explain the linking of Merlin to Arthur; in actuality Myrddin (Merlin) is linked to King Rhyderrch of Strathclyde, not to Clinoch; although as discussed previously it is likely that he would have had his own druid advisor. More on Scottish legends of Merlin are found in the entry for Queen Margaret. Similarly, St. Mungo is linked to Arthur through King Rhyderrch.
The legend would grow and grow. For example that Guinevere came from Perth is true when it is realised that that Scone (just outside Perth) was an ancient capital of Scotland and perthage is Welsh for hedge. The hedge would surround and protect the nation's sovereignty as Perth can be said to 'protect' Scone. Guinevere is probably just a representation of sovereignty. In this way, Arthur (the Ard Righ) would be 'married' to sovereignty.
Gildas states the Damnonia was a "lioness" and in another legend Guinvere is said to come from Leoness. This lioness just means that Damnonia at the time held sovereignty for the region. Hence Gildas denunciation of Constantine (Comgall) as a "whelp of the filthy lioness of Damnonia".
Damnonia (Strathclyde) held the sovereignity of Britain; the capital of Strathclyde was Dumbarton (Ail-Cluathe); Dumbarton was the capital of Britain. Arthur, the Ard Righ, was based in Dumbarton. Drumry , the King's Ridge Drum Righ, was probably named to emphasise the sovereignty of Strathclyde and would have been named in honour of the Ard Righ, Arthur. (There is more on Arthurian localities in Scotland in the entry for King Robert I.)
Conclusion
There are many theories of the identity of King Arthur, all of them upheld with passion and conviction. The theories can be generally split into two camps :- those based on "contemporary" references, and those based on legend inspired by Geoffrey of Monmouth and his ilk. (More on the legendary stories can be found in the entry for King William I.) The latter group can be effectively discounted; at best only considered as corroborating evidence for theories of the first group.
A strong argument of my theory is that I have based Arthur and his battles in a strategically defendable geographical area; Scotland and the north of England. A scattered battle campaign throughout the whole of Britain would be logistically difficult for a modern army to undertake and almost impossible for an army in the sixth century.
There are other theories that also restrict King Arthur to a defendable area, notably those placing Arthur in Wales, Cornwall or Lincolnshire. Lincolnshire gained fame as a favourite of Geoffrey of Monmouth, but with its fens, bogs and swamps would be an unlikely place for Arthur's battles, given many were sited near rivers. Cornwall and Wales are natural contenders given their P-Celtic history. Tintagel in Cornwall was suggested as a site for Camelot despite being built centuries after the timescale of Arthur. Wales has many associations with Arthur. I would suggest that these arose through the transplanting of the legend to Wales, as the language retreated from Scotland, so the customs, traditions and legends would follow.