Addressing the Galfridian Tradition of St. Illtud as King Arthur's Father

The Name "Illtud" on the Samson Cross, Llantwit Major (Llanilltud Fawr)

I've posted below the entire Appendix XIV from my book THE BEAR KING: ARTHUR AND THE IRISH IN WALES AND SOUTHERN ENGLAND.  This appendix is the culmination of a series of essays on St. Illtud as Arthur's father in the Galfridian tradition.

When I first realized that Uther Pendragon was beyond reasonable doubt a Welsh nickname for Illtud derived from Latin descriptors found in the saint's VITA, I was at first very excited.  For many years I had sought the "true identity" of Uther and, like so many others before me, I had failed miserably. Now I was sure I could make a good case for a historical Arthur, as I had a verifiable historical father for him.  And this father could be geographically fixed, and fit the necessary chronology.

Unfortunately, my excitement over this discovery soon began to dwindle and then dissipated entirely.  Why?  Because of two factors, primarily.  First, I was fairly certain Arthur's battles were those of Cerdic of Wessex (= Ceredig son of Cunedda, the 'bear king' of the Arth River in Ceredigion, whose ruling house contained several bear names).  Second, an Arthur who was the son of Illtud seemed to take away the Irish connection, which was critical to a proper identification of Arthur (as all subsequent Arthurs belong to Irish-founded dynasties in Britain).  Unless, of course, we allowed for Illtud's Brittany (Llydaw/Letavia) being for the broad part of the Usk Valley in Irish-founded Brycheiniog or an error for the Ui Liathain of southern Wales.  Evidence instead suggested rather strongly that Llydaw in this instance stood for the Vale of Leadon bordering of the ancient Welsh kingdom of Ercing.  Ercing has several early Arthurian associations and Illtud's mother came from there. Third, if Arthur were Illtud's son, I could not account for the name. Simply put, where would a British form of Roman Artorius come from in this context? For Ceredig, it could easily be a decknamen for an earlier Irish or British name or title meaning 'Bear-king.' If the Vale of Leadon were the point of origin for Illtud, we might be able to associate this family with the Roman period kingdom of the Dobunni, which was later supplanted by that of the Hwicce.  Barbury Castle, the "Bear's fort", was in Dobunni land and I have often wondered if Arthur's name might have something to do with that site.

What if, however, the Cerdic/Ceredig son of Cunedda battles had merely been appropriated for the glorification of Arthur son of Illtud? And what if Illtud did trace his ancestry to the Irish?  Could Arthur's name really be related to that of Barbury?

Before I consider these possibilities, it is worth asking another, perhaps, more critical question: if Uther Pendragon was not the father of Arthur, why did absolutely no one at all after Geoffrey counter the claim that he was?  Why did not even one authority cry foul?

From the standpoint of the Gwynedd author of the HISTORIA BRITTONUM, who first introduces us to Arthur in any detail, why would he have used Arthur for Ceredig at all?  I mean, all the royal families of NW Wales took great pride in claiming Cunedda and his sons as their ancestors.  The kingdom of Ceredigion was literally named for Ceredig son of Cunedda.  So why would the name Ceredig not have been used, if this was the person intended?  This makes no sense to me whatsoever.  The only possible reason for disguising Ceredig under another name/title is because the English claimed him as their founder of Wessex.  While this might be considered a suitable explanation for the name switch, it would represent an extremely bizarre attempt to hide Ceredig's true identity. 

Of course, the same could be said of many of the outlandish fictions of Geoffrey's pseudo-history.  But in the case of the very famous Arthur - whose story dominates the HISTORY OF THE KINGS OF BRITAIN - we cannot so easily ignore the established traditional account.  Is it feasible to consider that from the time of the 9th century sources mentioning Arthur, throughout the development of the more legendary material in the later period, the name of Arthur's father remained totally unknown or was at some point forgotten?  And that Geoffrey of Monmouth, discerning the lack of recorded paternity, simply borrowed Uther for the purpose?  And if he did borrow him, what rationale did he use to make such a choice?  Did he merely like the sound/signification of the name?

I've been wrestling with the possibility, therefore, that at least in this one respect, Geoffrey might be right.  That is, Illtud might really have been Arthur's father.

If he was, it would be necessary - after accepting a Hiberno-British line of descent for Illtud - to either strip Arthur of the Cerdic battles or to posit Arthur as Cerdic's opponent during those battles.  As Ceredig son of Cunedda fought against the Ui Liathain and it is not impossible that Illtud's Llydaw is a mistaken reference to this Irish tribe, it would make sense to view Arthur and Ceredig as enemies.  With Arthur attached through family to the old Dobunni kingdom, he may well have fought the Gewissei (Cunedda and his family/followers) in southern England. Modred/Medraut (see my book THE KING OF STONEHENGE: MODRED AND THE DEFENSE OF DARK AGE BRITAIN) may not have been adversaries, but allies.

All of this I outlined elsewhere, but the more I consider Arthur as the son of Illtud, the more convinced I become that he may have been exactly that.  The bear personal and place-names of the Kingdom of Ceredigion may have made someone think of the name Arthur and thus the battles of Ceredig were transferred to the latter.

And where does this leave my contention that Barbury may have either been named for Arthur by the English or have contributed to his name?  Again, I'm not sure.  It is tempting to place emphasis on this Wiltshire hillfort, as the Liddington Badbury is nearby.  But I'm pretty certain Gildas's Badon is NOT Badbury, but was instead, originally,  reference to the ANGLO-SAXON CHRONICLE's battle of c. 501 A.D. featuring Bieda.  It was not a famous battle, but only became so because the saintly Gildas was born in that year.  The spelling was wrongly confused with that of Bath, a battle fought much later, supposedly by the Gewissei. Still, Barbury might have been a sort of forward base for Arthur if he were fighting the Saxons and the Gewissei allies in the south.  Arthur is most strongly linked to Cornwall (Cernyw; cf. Cornovii) in Welsh tradition, and the Roman period Durocornovium, 'Fort of the Cornovii', was situated right next to Liddington Castle.

Barbury Castle

***

APPENDIX XIV:

THE TRUE IDENTITY OF UTHER PENDRAGON

In my book THE ARTHUR OF HISTORY, I had treated briefly of the Arthurian battles of the Welsh poem ‘Pa Gur.’  But what I neglected was the fairly obvious point made by the poem's placement of the 'vythneint' ("predatory birds", a metaphor for warriors) at Elei (valley of the River Ely in Glamorgan).  Why might this placement be so important?

Because one of them, viz. Mabon son of Modron, is called the servant (guas/gwas) of Uther Pendragon.

There is an implied sense in this passage that I failed to pick up on in the past.  Simply put, if Mabon is of Elei and he is the servant of Uther, then might we not infer that Elei belonged to Uther?  In other words, Mabon was the servant of Uther at Elei.  If this is not what is meant, then it if difficult to explain why it was felt necessary to tell us that Mabon was Uther's servant in this particular context.

So what, exactly, is in Elei?  Well, there is the impressive Caerau hillfort (http://www.coflein.gov.uk/en/site/94517/details/caerau-hillfortcaerau-campcaerau-ely), an oppidum of the Silures tribe.  Unfortunately, there is no evidence that this site continued to be inhabited after the Roman invasion and consolidation of the region.

However, just south of Caerau and only a couple of kilometers from the Ely River is the Dinas Powys hillfort.  The story here is completely different.  We have ample evidence for early medieval use (http://www.coflein.gov.uk/en/site/301314/details/dinas-powys-fort-previously-cwm-george-or-cwrt-yr-ala-camp).  It "may have been established as late as the Roman period."

Now, of course, we have to be careful here.  Mabon is a god - not a human servant.  And the 'Pa Gur' is replete with battles against monsters and supernatural entities.  These contests range all over Britain, and so are quite fabulous in nature.  What weight, therefore, can we place on an oblique reference pertaining to Uther's residing at Dinas Powys in Ely?

There is nothing in and of itself that is marvelous about Dinas Powys - other than the fact that it was occupied during the Arthurian period.  The real question becomes "Why would the poet have placed Uther there?"

One possible reason might be that the Cadoxton River runs at the eastern foot of the hillfort.  This stream bears the name of St. Cadog, whose late 11th century (?) VITA includes a story about Arthur.  Still, Arthur is nowhere in the Life said to be related to Cadog.

It would appear the only thing that can be said about Uther at Dinas Powys is that at the time of the composing of the 'Pa Gur' a tradition may have existed which knew of this hillfort as the fortress of Arthur's father.  If this tradition is historically sound, then the 'Pa Gur' preserves the only extant notice of Uther's geographical whereabouts.

For a nice summary of the excavations at and theories regarding Dinas Powys, see

http://repository.uwtsd.ac.uk/378/1/Helen%20Anderson.pdf

In the VITA of St. Illtud (cousin of Arthur), once the saint has visited the king's court he travels to King Pawl Penychen.  Penychen was that part of Glamorgan between the Thaw and the Taff, wherein is situated Dinas Powys.

Illtud the soldier, b. c. 470 A.D. - eventually to become the famous St. Illtud - ended up becoming Pawl’s military commander.  There is the strong possibility that Pawl's fort was Dinas Powys in Penychen.

A surprise awaited me when I looked into St. Illtud in more detail.  He was referred to as 'farchog', "knight", and filwr, 'soldier/warrior', as well as  'princeps militie' (militum princeps) and magister militum (https://freidok.uni-freiburg.de/dnb/download/6837).

Chapter 2 of the VITA SANCTI ILTUTI calls the living Illtud "miles magnificus."  We may compare this with Uther [Pen]dragon (where dragon has the usual metaphorical meaning of “warrior”):

W. uthr

fearful, dreadful, awful, terrible, tremendous, mighty, overbearing, cruel; wonderful, wondrous, astonishing, excellent. 

L. magnific.us               

splendid/excellent/sumptuous/magnificent/stately; noble/eminent; proud/boastful

But, even better, at the end of his VITA we are told of a 'terrible soldier/warrior', who though of a heavenly nature and left unnamed, is plainly the returning spirit of the old soldier Illtud, out to retrieve his stolen bell:

From the Life of St. Illtud:

In meridiana autem hora, dum rex quiesceret in tentorio campestri in planicie affixo, diuidereturque maxima predatio, uisum est regi quod quidam terribilis miles suum pectus lancea perforasset, atque post perforationem nemini uisum. [...] Timoratus imperauit sacrilego exercitui reddere Deo et sanctissimo Iltuto totam predationem, promittens deinceps emendationem, atque in honore eiusdem sancti edificauit templum, et seruentibus in templo concessit in quo stetit territorium. Hec emendation tamen profuit suo spiritui, recessit enim ab hoc seculo .ix.no die propter nequitie uindictam.

At the hour of noon, while the king rested in a field-tent put up on a plain, and the immense booty was being divided, it seemed to the king that some terrible soldier had pierced his breast with a spear, and after the piercing he was seen of none. […] Full of dread he bade his sacrilegious army to restore to God and to the most holy Illtud all the plunder, promising thereafter amendment, and in honour of the same saint he built a church, and to those serving in the church he granted territory in which it stood. This amendment, however, profited his spirit, for he departed from this life on the ninth day as punishment for his wickedness (VI, §25).

We may thus place Illtud as the terrible warrior at Dinas Powys - the same place Uther [Pen]dragon, the Terrible [Chief-]warrior, is placed in the 'Pa Gur.'

Dinas Powys Hillfort

[NOTE: Uther Pendragon appears to originally have been called simply Uther Dragon. We know this is so by looking more closely at the guide-title of the ‘Uther Pen’ poem.  After receiving false or conflicting or just plain confusing information on this from several sources, I finally asked Dr. Maredudd ap Huw, Manuscripts Librarian, Department of Collection Services at the National Library of Wales.

Dr. Huw’s response, in full:

“Firstly, I confirm that there is no ellipsis indicated in the manuscript, and that the gloss (or more correctly guide-title) reads 'mar. vthyr dragon.'

Secondly, on looking at the manuscript, it appears that the guide-title is written by the main scribe to inform the rubricator, who subsequently added the abbreviated title. The red ink of ‘n’ in ‘pen’ appears to cover the letter ‘d’ of ‘dragon’.

I regret that I am not in a position to speculate as to why the rubricator did not follow the exact wording offered by the scribe in the guide-title.”

This last is an important observation. The rubricator (called such because he used red ink) wrote ‘marvnat vthyr pen.’ for the main scribe’s ‘mar. vthyr dragon.’]

But how can Illtud be Arthur's father?  The Welsh sources insist he was Arthur's cousin.  Their mother's were said to be sisters, both daughters of Anblaud (later Amlawdd) Wledig of Ercing, a character whom Brinley F. Roberts regarded as fictitious:

“Anlawdd Wledig seems to be a function rather than a person. He is an ‘empty’ character ... who exists merely so that his daughters may be the mothers of heroes who are all, therefore, cousins of Arthur.”  (see P.C. Bartram’s A CLASSICAL WELSH DICTIONARY)

Illtud's father was Bicanus of Letavia/Llydaw, not here Brittany, but instead probably a designation for the Vale of Leadon between the Wye and the Severn, bordering on Anblaud’s Ercing. The River Leadon (early forms Ledene, Leden, from OBrit *litano-; cf. Welsh llydan) contains the same Celtic root as Llydaw. According to the ever-unreliable Geoffrey of Monmouth, Uther came to Ercing from Brittany.   Illtud's wife Trynihid is also said to have been from Brittany.

Traditionally, this particular Llydaw is said to be found in Wales - and, in particular, somewhere in the vicinity of the Brycheiniog where we find two supposed graves for Illtud. The saint was said to have been buried in Letavia/Llydaw, so the fact that we find two prehistoric tombs bearing his name to the west and east of Brecon is surely significant.

One grave is near Defynnog and Mynydd Illtud, the Bedd Gwyl Illtud or Grave of Illtud's Festival, and the other is Ty Illtud or House of Illtud north of Llanhamlach.

I decided to see how Llydaw (from a Celtic root meaning 'broad' or 'wide') could possibly refer to this region.  What I found, rather surprisingly, were many references to the BROAD valley of the River Usk at Brecon.  While I could cite all of these, I hope the following will suffice.  It is drawn from Charles Thomas's AND SHALL THESE MUTE STONES SPEAK?, which discusses the Irish-founded kingdom of Brycheiniog in some detail.

"The centre [of the Kingdom of Brycheiniog] is modern Brecon, at the south end of the broad corridor between mountains running north-north-east up to the river Wye at Glasbury."

In other words, the Usk Valley was unusually wide or broad at this point, and the Welsh word llydaw (from a well-attested Celtic root meaning wide or broad or extensive) may well have been applied to it as a descriptive term, which in time came to be confused for an actual place-name.

Having read these many references to the wide valley of the Usk at Brecon, and having viewed photos and studied topographical maps, I'm now convinced that this location could, in fact, be the "Llydaw" of Illtud.  If this was the place, we could say that as a man of Brycheiniog, he most likely had Irish blood in his veins.  If he were, in actuality, the father of Arthur - as tradition insists - then we can account for the fact that the name Arthur was later used only for royal sons of Irish-descended dynasties in Britain.

Yet a third possibility exists for Illtud’s Llydaw.  In Cormac's Glossary, the fort of the Ui Liathain among the Cornish Britons is called 'dind map Lethain.'  Lethain is a very common early spelling given to Irish lethan, 'broad, wide, wide-spread', the cognate of Leadon and from the same root that yielded Llydaw, Letavia (Brittany).  Cf. Welsh llydan.  According to Professor Jurgen Uhlich of Trinity College, Dublin, "lethain is simply one of several regular case forms of lethan, i.e. gen. sg. m./n., dat/acc. sg. fem. or nom pl. m.".

I also find Liathain in Irish Latin as 'Lethani' (Vita Sancta Columba).

That the two words were mistaken for each other in Irish is shown in COIR ANMANN or THE FITNESS OF NAMES (H.3.18, p. 565a):

50. Fedlimith Uillethan, that is, Fedlimith Ua-Liathain, that is in Húi Liathain he was reared. Hence he was named Fedlimith Uillethan. Or Fedlimith Ollethan i.e. huge (oll) and broad (lethan) was he: thence he was named.

Place-names containing these words may also have been substituted for each other.  In Geoffrey Keating's THE HISTORY OF IRELAND FROM THE EARLIEST PERIOD TO THE ENGLISH INVASION, I find "Drom Liathain (Drum Lee-hawin), is probably Drom Lethan (Drum Lahan), now Drumlane, co. Cavan."  This is confirmed in Edmund Hogan's ONOMASTICON GOEDELICUM: "d. liatháin Fm. i. 44; ¶  prob. for D. Leathan, now Drumlahan or Drumlane, c. Cav.; ¶  Eochaid fought against the Ernu and the Mairthine at D. L., Hk. 324, Lec. 63, 578, Sb. 4 a 1, K. 131 b, Lg. 91; ¶  most prob. in Mun."  Drum/Druim Leathan is 'Broad Ridge' (https://www.logainm.ie/en/5248).

A truly extensive search might well uncover other examples.

Francis J. Byne, in his magisterial IRISH KINGS AND HIGH-KINGS (p. 184) says "Lethain is the archaic form of Liathain."

Charles Thomas in AND SHALL THESE MUTE STONES SPEAK? mentions a Liteni on an ogam stone in Co. Waterford.  He says "Litenos may stand for the tribal eponym [of the Liathan]."

The Liathain tribal name is from an epithet whose root is the word for 'grey' in the Irish language and is not related to lethan/lethain.

From Professor Jurgen Uhlich at the Department of Irish and Celtic languages, Trinity College, Dublin, Ireland:

"These are actually two different words that cannot be confused: líath, gen. sg. m. léith, etc., has an original long ē, while the -e- of lethan is short, < *i and corresponding to Gaul. litano- etc. Ui Liathain is thus for Ui Líatháin, with the common suffix -án, and the Primitive Irish equivalent would be, written in Ogam, *LETAGNI, i.e. nothing to do with ‘broad’, which would have given *Ui Lethain < *LETANI lowered from *LITANI. The reported reading in CIIC no. 273 is actually ‘LIT[ENI]’, which could not be ‘broad’ either, and Macalister’s sketch appears to read LITOVI instead (though perhaps meant to be damaged, i.e. two dots might be intended to be missing for an E, and one stroke for an N). So in short, the ía strictly rules out your proposed equation."

However, it would have been very easy to have intentionally or accidentally used a spelling of Lethain for Liathain and thus created a "Brittany" within Wales.

Illtud is not said to have had any children.

A NOTE ON GWYNLLYW, BROTHER OF PAWL PENYCHEN

Pawl Penychen's brother Gwynllyw, who features largely in the Life of St. Cadog in connection with Arthur, was also described as terrible in a military sense.  From the Life of St. Gwynllyw:

Deinde regressi sunt onerati ad naues [...] Dum hinc inciperent uela erigere [...] uidebant unum terribilem equitante die et nocte, et persequentem illos ex omni parte. Eques iste terribilis sanctus erat Gunlyu, qui celitus missus fuerat, ut obsisteret sacrilegis.

Then they returned to their ships burdened […] When from this place they began to hoist sails […] they saw a single being, one terrible, riding day and night, and pursuing them on every side. That terrible rider was holy Gwynllyw, who had been sent from heaven to withstand the sacrilegious ones
(VGu §12).

However, Gwynllyw's territory lay east of the Taff, while that of Pawl extended west of that river.  Gwynllyw, therefore, did not rule from Dinas Powys.

THE SAWYL CONNECTION

Another argument in favor of seeing Uther Pendragon as Illtud is found in a comparison of an early elegy poem and a passage from Geoffrey of Monmouth’s HISTORY OF THE KINGS OF BRITAIN.

The poem in question, the MARWNAT VTHYR PEN or 'Death-Song of Uther Pen[dragon]', is best treated of through Marged Haycock's recent translation. This is what Professor Haycock has in her notes to Line 7 of this elegy:

 7 eil kawyl yn ardu G emends kawyl > Sawyl, the personal name (from Samuelis
via *Safwyl). Sawyl Ben Uchel is named with Pasgen and Rhun as one of the
Three Arrogant Men, Triad 23, as a combative tyrant in Vita Cadoci (VSB 58);
and in CO 344-5. Samuil Pennissel in genealogies, EWGT 12 (later Benuchel),
Irish sources, and in Geoffrey of Monmouth. Other Sawyls include a son of
Llywarch, and the saint commemorated in Llansawel: see further TYP3 496,
WCD 581 and CO 104. Ardu ‘darkness, gloom; dark, dreadful (GPC), sometimes
collocated with afyrdwl ‘sad; sadness’ (see G, GPC).

Initially, I refused to get too excited about Uther calling himself a 'second Samuel' (the first, presumably, being the Biblical prophet of that name).  I mean, this was, after all, an emendation.  However, I asked Welsh language expert Dr. Simon Rodway of The University of Wales about the authority who made this emendation - one that was accepted by Haycock herself.  Our discussion on this matter ran as follows:

"Geirfa Barddoniaeth Gynnar Gymraeg, by John Lloyd-Jones

Cited several times by Marged Haycock in her edition of the Uther poem, and  she adopts many of his emendations.

A trustworthy, well-respected source, in your opinion?  Or is his work somewhat outdated or even obsolete?"

"It’s a very good piece of work, which I often use. It’s much more comprehensive than GPC [Geiriadur Prifysgol Cymru, 'Dictionary of the Welsh Language']."

Such an unqualified, professional academic opinion of Lloyd-Jones changed everything!

As for how the error could have occurred, Dr. Rodway suggested the following scenario:

"It can’t be a case of miscopying a letter, but it could be eye-skip - when a copyist’s eye skips inadvertently to another nearby word resulting in an error.  In this case, he would have eye-skipped to the preceding line's 'kawell' to get the /k-/ fronting what should have been 'sawyl'.  Was not an uncommon error, so quite plausible.  Also, kawell and kawyl are unlikely to be the same word.  The poets avoided repeating words in consecutive lines. In cases where this does occur (v rare) it could be scribal error."

I had tried to use this information to connect Uther Pendragon with Sawyl Benisel (later Ben Uchel) of the North.  Such an attempt ultimately proved nonviable.

But just recently I reread the ever-unreliable Geoffrey of Monmouth, whose work cast a long shadow - even upon what had been preexisting Welsh tradition concerning Arthur.  And I was astonished to encounter this episode:

CHAP. VII.—Hengist is beheaded by Eldol.

AURELIUS, after this victory, took the city of Conan above-mentioned, and stayed there three days. During this time he gave orders for the burial of the slain, for curing the wounded, and for the ease and refreshment of his forces that were fatigued. Then he called a council of his principal officers, to deliberate what was to be done with Hengist. There was present at the assembly Eldad, bishop of Gloucester, and brother of Eldol, a prelate of very great wisdom and piety. As soon as he beheld Hengist standing in the king's presence, he demanded silence, and said, "Though all should be unanimous for setting him at liberty, yet would I cut him to pieces. The prophet Samuel is my warrant, who when he had Agag, king of Amalek, in his power, hewed him in pieces, saying, As thy sword hath made women childless, so shall thy mother be childless among women. Do the same to Hengist, who is a second Agag." Accordingly Eldol took his sword, and drew him out of the city, and then cut off his head. But Aurelius, who showed moderation in all his conduct, commanded him to be buried and a heap of earth to be raised over his body, according to the custom of the pagans.

This Eldad(us) of Gloucester is Illtud of Glywysing (Glywys being the eponym of Caer Gloyw or Gloucester).  He is here likening himself to the Biblical Samuel, Sawyl in Welsh.

Combined with everything else I've come up with that seems to show Uther = Illtud, this apparent correspondence of the Elegy's 'eil Sawyl' or "second Samuel" with Illtud appearing symbolically as a 'second Samuel' is truly remarkable.

UTHER, THE FALSE FATHER OF ARTHUR

Although I am confident of my identification of Uther Pendragon with St. Illtud, the question remains: was he really Arthur's father?

Information on Uther prior to Geoffrey of Monmouth's fictional HISTORY OF THE KINGS OF BRITAIN is scarce.  To quote from the entry on Uther in P.C. Bartram's A CLASSICAL WELSH DICTIONARY:

UTHR BENDRAGON, father of Arthur. (445) ‘U. Chief Warleader’. Evidence that Uthr Bendragon was known to the Welsh before the time of Geoffrey of Monmouth is plentiful, but it does not tell us much about the pre-Geoffrey legend. He is mentioned in the poem ‘Who is the porter’ in the Black Book of Carmarthen, a dialogue between Arthur, Cai and Glewlwyd Gafaelfawr. Mabon ap Modron, one of the companions of Arthur, was guas Uthir Pendragon, ‘Servant of Uthr Bendragon’ (BBC 94, ll.6-7). An early triad (TYP no.28) tells of the Enchantment of Uthr Bendragon as being one of the ‘Three Great Enchantments’ of Ynys Prydain, and says that he taught the enchantment to Menw ap Teirgwaedd. In the Book of Taliesin (BT 71) there is a poem entitled Marwnat Vthyr Pen to which Dragon has been added in the margin in a later hand. This expansion is probably justified, since, among much that is obscure, the poem contains a reference to Arthur: ‘I have shared my refuge, a ninth share in Arthur's valour’ (BT 71, 15-16). See AoW 53. All these references bring Uthr into the Arthurian orbit (TYP p.521). Madog ab Uthr is mentioned in the Book of Taliesin (BT 66) and Eliwlod ap Madog ab Uthr is described as nephew of Arthur in a poem which shows no dependence on Geoffrey of Monmouth. See s.nn. Eliwlod, Madog. This is evidence that Uthr was regarded as father of Arthur in pre-Geoffrey legend. In two manuscripts of the Historia Brittonum (Mommsen's C, L, 12th and 13th centuries), §56, which lists Arthur's battles, contains a gloss after the words ipse dux erat bellorum: Mab Uter Britannice, id est filius horribilis Latine, quoniam a pueritia sua crudelis fuit, ‘In British Mab Uter, that is in Latin terrible son, because from his youth he was cruel’. According to Professor Jarman there is here a deliberate pun on the word uthr, which can be either an adjective (‘terrible’) or a proper name. The author of the gloss could have been familiar with Geoffrey of Monmouth's ‘Historia’.  See A.O.H.Jarman in Llên Cymru, II (1952) p.128; J.J.Parry in Speculum, 13 (1938) pp.276 f. See further TYP pp.520-3.

The most important phrase in this entry is "This is evidence that Uthr was regarded as father of Arthur in pre-Geoffrey legend." The context is the 'Dialogue' poem.  Unfortunately, as Professor Patrick Sims-Williams discusses in his "The Early Welsh Arthurian Poems" (in THE ARTHUR OF THE WELSH), the 'Dialogue' is preserved only in fourteenth century or later MSS., but may be as early as the twelfth century.  Geoffrey of Monmouth wrote his HISTORY c. 1138, i.e. in the first half of the 12th century.  Thus there is no way we can know whether the 'Dialogue' poem was influenced by Geoffrey's claim that Arthur's father was Uther Pendragon.

The reference to Arthur in the Uther elegy is, like many lines of this poem, difficult and obscure.  Here are the relevant lines and accompanying note from Marged Haycock's recent translation:

13. Neu vi a rannwys vy echlessur:
It was I who shared my stronghold:

14. nawuetran yg gwrhyt Arthur.
Arthur has a [mere] ninth of my valour.

Note to Line14

nawuetran yg gwrhyt Arthur

Nawuetran ‘ninth part’ with yg gwrhyt understood as ‘of my valour’ (gwryt ~ gwrhyt). Arthur has a ninth part of the speaker’s valour. This seems to have more point than ‘I have shared my refuge, a ninth share in Arthur’s valour’, TYP3 513, AW 53. Gwrhyt ‘measure’ is not wholly impossible — ‘one of the nine divisions [done] according to the Arthurian measure/fathom’, etc., or ‘a ninth part is in [a place] called Arthur’s Measure or Span’, the latter like Gwrhyt Kei discussed TYP3 311, and other Gwryd names discussed G 709-10. The phrase is exactly the same as in §18.30 (Preideu Annwfyn) tra Chaer Wydyr ny welsynt wrhyt Arthur.

This is no way implies Arthur is Uther's son.  As I've mentioned before, Arthur here may be the usual paragon of military virtue to whom Uther is being compared, much as the warrior Gwawrddur is compared (unfavorably) to Arthur in Line  972 of the "Goddodin."  Yet someone like Geoffrey of Monmouth may have come across this 'death-song' and decided to use it as the exceedingly slender basis for making Uther Arthur's father.

Nothing in the VITA of St. Illtud suggests that he was Arthur's father.  In fact, it is pointedly stated in that hagiographical work that Illtud is Arthur's cousin.  So if Illtud were Arthur's father, the fact was later altered in the tradition which preferred to make of this terrible warrior a Christian saint.

All in all, the evidence in support of Uther as Arthur's father is quite poor. Let us not forget that it was Geoffrey of Monmouth who made Gorlois out of an epithet (the gorlassar of the “Marwnat Vthr Ben poem) belonging to Uther.  This kind of loose, creative treatment of the material does not lend itself to the credibility of the author when it comes to properly identifying Arthur’s sire.