The earliest Vita Gildae was written in Brittany about the end of the 10th century by a monk of Buys. According to this Vita, Gildas, who was the son of Caw o Brydyn, that is, Caw of Pictland, was born in the regio of Arecluta, where his father reigned as king. Arecluta, later Arglud, means on or opposite the Clyde, just as Arvon means on or opposite Mon (Anglesey). The Vita describes the regio of Arecluta as a part of Britain, which took its name from the river Clut (Clyde) "by which that regio is for the most part watered." The family of Gildas, therefore, originated near the western half of the Wall of Antonine.
Caw is variously described in the vitae Gildae as rex Scotiae, a king of Scotia, rex Albaniae, a king of Albania, and rex Pictorum, a king of the Picts. The latter is the nearest equivalent of the oldest name by which he is known in Welsh, namely, Cau Pritdin. This last is found in the Vita 8. Cadoci, by far the most valuable of our Welsh vitae sanctorum, where Cau cognomine Pritdin is said to have reigned for many years ultra montem Bannauc. Mr. Skene and Mr. Phillimore see the name Bannauc in the place-name Carmunnock, near Glasgow, and on this account would identify Mons Bannauc with the Cathkin Hills. In this case the regio of Arecluta would be in modern Renfrewshire.
Caw o Brydyn is also known in Welsh manuscript literature as Caw o Dwrcelyn, Caw of Twrcelyn, a regio in the north of Anglesey, and at one time one of the six cymwds of the island. He is repeatedly so called in Dr. Gwenogvryn Evans's Report on M83. in Welsh. "It is not clear how Caw got the name of 'Caw of Twrcelyn' (in Anglesey), see Table 5, where are also given the names of his seventeen or twenty-one children, some of them daughters, and many of them commemorated as saints in Mon (Anglesey).
The association of the family of Caw, in literature, with Twrcelyn in Anglesey is as early as the Breton Vita Gildae itself, for it states how that two of his sons, Egreas and Alleccus, together with a daughter Peteova, withdrew to a remote part where each of them founded an oratory. These three oratories were near one another, that of the virgin sister being in the center. Thus the two brothers were able to sing mass for their sister every day alternately. As they died they were buried in their respective oratories, which, in the time that the monk of Buys was writing, were famous and illustrious for their constant miracles. The sites of the oratories of Egreas and Alleccus are represented to day by the churches of Llaneugrad and Llanallgo, both situated within the ancient cymwd of Twrcelyn in Anglesey, and about half-a-mile apart. The oratory of Peteova must have lain between them.
When St. Cadog met Cau Pritdin, the latter was no longer reigning in the regio of Arecluta. He had come away from beyond Mons Bannauc "ad has oras", to these borders or coasts, where St. Cadog had settled for a time to build a monastery and to convert pagans. The legend of St. Cadog's raising Caw from death and hell would seem as though Caw himself were a pagan, but, however that may be, Caw is made to become a disciple of St. Cadog, and to remain in that place till his death ("ad ipsius obitum illic"). Consequently Caw never returned to settle in his old regio and regnum of Arecluta. The passage ends with the significant statement that Caw received a grant of twenty-four vills from the Albanorum reguli ; in other words, Caw who had formerly been a king beyond Mons Bannauc, in the little regio of Arecluta, received a new little regnum of twenty-four vills. And as Caw lived the last years of his life near Cadog's monastery, it is practically certain that that monastery was surrounded by this little regnum.
It is clear that to the writer of the Vita St. Cadoci all this took place in Scotland, where he has made Cadog go on pilgrimage to St. Andrew's in imitation of his former pilgrimages to Jerusalem and Rome. But as St. Andrew's was founded centuries after Cadog's time, this can only be a gloss on the original account. All that we can be certain of is that Cadog went amongst the Albani or Picts ; that he met Caw of Pictland, who became his disciple, and died near the monastery which Cadog had founded ; and that Caw had a little kingdom of twenty-four vills in that place, which was not Arecluta. The writer and compiler of the Vita St. Cadoci, seeing that Cadog had gone amongst the Picts, thought that this must be Scotland, and added his explanation of a pilgrimage to St. Andrews. But in St. Cadog's time there were "Picts" in southern Britain, to wit, between the River Dee and the River Teivi, where Cunedda and his sons, "gwyr y gogledd", had settled from southern Scotland. If, therefore, we look for Cadog's monastery, which he founded among the Picts, in North Wales and Cardiganshire, we find that in the whole of this district there is only one, and that one is in the cymwd of Twrcelyn in Anglesey. It is still called Llangadog, i.e., the llan or monasterium of Cadog, being situated about the middle of Twrcelyn, and not three miles distant from the once illustrious oratories of Egreas, Alleccus and the virgin Peteova, the children of Caw of Pictland.
There can then be little or no doubt that Cau Pritdin, the father of St. Gildas, was a Pictish raider, who in the fifth century came from the banks of the Clyde "ad has oras", to these coasts of Anglesey, "causa diripiendi easdem atque vastandi", for the purpose of plundering and ravaging the same, as Caw himself is made to confess in the Vita St Cadoci ; and that he established himself in the district of Twrcelyn, with which his name was afterwards associated, where he became a disciple of St. Cadog at the new monastery of Llangadog in Twrcelyn, and where he ruled as king over a little regnum of twenty-four vills till his death.
It remains to be said that the pedigree of Cau Pritdin appears to be unknown. No ancient or reliable document seems to give it. Only in late post-reformation and very much doctored writings, contained in the Iolo MSS., do we find a table of ancestry provided for him, which, however, is not that of a Pictish raider, but of a quite respectable Devonian royal house, namely, the line of Geraint ab Erbin. Geraint had a son called Cadwy, with whose name that of Caw of Pictland has been confounded.
The stone in Ruthin where Arthur cut off the head of Huail, son of Caw.
According to the Breton Vita Gildae, Caw was succeeded as king by his warlike son Cuillus. In the Vita Gildae of Caradog of Llangarvan, who was a contemporary of Geoffrey of Monmouth, Caw is given twenty-four sons, victorious warriors, one of whom was Gildas. That Gildas, however, is not to be counted for a victorious warrior appears lower down where his twenty-three brothers are described as constantly resisting Arthur, "the king of the whole of Great Britain". The eldest of them is called Hueil who would submit to no king, not even to Arthur, a statement which is echoed in the story of Kulhwch and Olwen where, in the list of Caw's children, it is remarked of Hueil that he never made a request at the hand of a lord.
Hueil, says Caradog, used to sally forth from "Scotia" to ravage and plunder, and this so successfully and so frequently that Arthur had to run him to earth, which he did in the island of "Minau" or "Mynau". [This is usually supposed to be the Isle of Man, and Caradog may have intended it as such, but is most likely to be in Mon (Angelsey). The animosity between Arthur and Hueil is also echoed in the story of Kulhwch and Olwen, where it is ascribed to the fact that Hueil had stabbed Gwydre, his own sister's son. [It may be stated that according to this story Arthur himself had a son called Gwydre, whose death is ascribed to the boar Twrch Trwyth at the same spot where Gwarthegyd the son of Caw was also killed by the boar.]
The Cuillus of the Breton Vita is generally identified with the Hueil of the Welsh Vita ; and if Egreas and Alleccus may stand for Eugrad and Allgo, so no doubt may Cuillus for Hueil. Hueil, however, according to Caradog, never became king, whereas Cuillus succeeded his father in the kingdom. It should be stated that among Caw's children, as recorded in Kulhwch and Olwen, there appears one called Celin, who may possibly be the Cuillus of the Breton Vita Gildae, especially if it could be shewn that he gave his name to Twrcelyn, Angelsey.
There is the absurb story of Hueil being beheaded by Arthur for exposing him on the dance floor when Arthur, having disguised himself as woman, was dancing with a girl friend. The truth that Hueil had stabbed Gwydre, his own sister's son, has been turned into a fable requiring Arthur to dress to as a woman! Sounds like a Gildas story.