Sunday, July 28, 2024

Arthur Son of Bicoir and the Slaying of Mongan Son of Fiachna

   
Arberth in Penbro


Long ago, I demonstrated that the Briton Arthur son of Bicoir was, in fact, Arthur son of Petuir of Dyfed.



What I had not fully explored is the reason why Arthur son of Petr/Pedr of Dyfed was linked to Kintyre in the Irish sources.

I think this is pretty obvious: the ancient and, presumably, Dark Age capital of Dyfed was Arberth in Penbro. Penbro, like Irish Kintyre, means Land's End.  Pen and Kin are cognates, and Welsh bro is found in its Irish form as OIr. mruig, MIr. bruig.

We have god reason for thinking the Dark Age Dyfed center was at or very near Arberth because of the survival of the Voteporigas stone:


"CASTEL-DAUYRAN (CASTELL-DWYRAN or DYRAM,) a chapelry, partly in the parish of KILMAENLLWYD, lower division of the hundred of DERRLYS, county of CARMARTHEN, partly in the hundred of DUNGLEDDY, county of PEMBROKE, SOUTH WALES, 4 1/2 miles (N.E.) from Narberth


Rhys/1896, 108--110, records that the stone had originally stood at Castell Dwyran...

Voteporigas was the great-grandfather of Arthur of Dyfed. The latter is thought (see Bartrum) to have been born c. 560. Mongan son of Fiachna was supposedly killed by Arthur son of Pedr in 625.  The stone (elsewhere referred to as a dragon stone or piece of pitchstone, which was restricted geologically to the Isle of Arran next to Kintyre) Arthur uses to kill Mongan may be a folk reflection of the name Pedr or Petrus.

Two questions need to be answered. First, if Arthur son of Pedr has been wrongly placed in Kintyre, how did this error come about? And, two, how did the name Arthur end up in Dyfed among the Deisi-descended royal dynasty?

It is possible, I suppose, that the name Arthur was confused with the name of the location of Mongan's grave:

U625.2
Áedán son of Cumuscach and Colmán son of Comgallán migrate to the Lord; and Rónán son of Tuathal, king of Ind Airthir, and Mongán, son of Fiachna of Lurga, die.

1] Remarkable are the four over whom it has closed without recall,
2] The earth of Cluain Airthir churchyard today:
3] Cormac the Handsome,
4] And Illann son of Fiachu.
1] The other two—
2] Many territories do service to them—
3] Are Mongán son of Fiachna of Lurga,
4] And Rónán son of Tuathal.


Cluain Airthir has been identified:

c. airthir
7 bps. of, Ll. 374, I. 110 b 1; ¶ 7 sts. of, Lb. 24; ¶ Fionntan of, Ai. 150 b; ¶ now Magheracloone, c. Mon., Ch. 78, Au. i. 94, Mi., Cri.; ¶ Cailcú of, Mt. 35, Ll. 363; ¶ = Caelchú ó Lúi Airthir, Fg. 182; ¶ Mongan mac Fiachnae, lord of C. Airrthir, Hb. 64

https://research.ucc.ie/doi/locus/C

Airthir (airther) means "eastern."

But this seems a bit far-fetched.

Instead, I think we must look to the second question: why did Pedr of Dyfed name his son Arthur? 

I have recently shown that the name Arthur apparently originated with Sawyl Benisel of Ribchester, and that it found its way into the Dalriadan royal house via Dal Fiatach connections:


Now Mongan belonged to the Dal nAraide in NE Ireland. To the north of the Dal nAraide were the Dal Riata, who founded Dalriada in Scotland. To the south of Dal Araide were the Dal Fiatach. These tribal groups were variously allied with each other or fighting against each other.  The best recent account of the interactions of these kingdoms during the floruit of Mongan comes from pp. 4-5 of John Bannerman's STUDIES OF THE HISTORY OF DALRIADA:




The poem on the death of Mongan tells us the warriors who kill him were in Kintyre.  Or, at least, they came from Kintyre:

T627.6
Mongan son of Fiachna Lurgan, stricken with a stone by Artur son of Bicoir Britone died. Whence Bec Boirche said:

Cold is the wind over Islay;
There are warriors in Cantyre,
They will commit a cruel deed therefor,
They will kill Mongan son of Fiachna.


If Mongan's killers really originated from Kintyre, then they were Dalriadans - that much is clear.  Yet this scenario is impossible to square with what appears to be a steady alliance between the Dal nAraide and the Dal Riata.

But what if Kintyre in the Irish Annal is an error for Penbro?  What if Pedr of Dyfed had married a Dal Fiatach princess, just as Sawyl Benisel had?  And the name Arthur had come from the Dal Fiatach into the Dyfed royal house?

The year dates for the death of Mongan and the death of his father Fiachna mac Baetain fall within a year of each other.  One finds, when going over the annals, that sometimes the same event is entered for different years.  Suppose Mongan died with his father at Leithat Midind, and Arthur son of Pedr was on the side of the Dal Fiatach king Fiachna mac Demmain?  An Arthur from Penbro could easily have been confused for the various Dalriadan Arthurs (Arthur son of Aedan or Conaing and Arthur grandfather of Feradach).

This solution to the Arthur son of Bicoir problem is particularly elegant in that it both accounts for how a Dyfed king could have been involved in warfare in the North as well as accounting for how the Arthur name came to be present in southwest Wales.  Such a solution must, of course, remain purely speculative as we lack any genealogical information regarding Pedr of Dyfed's wife and queen. 


































































Wednesday, July 24, 2024

WHY SAWYL BENUCHEL'S GRAVE IS AT ALLT CUNEDDA



I have recently suggested that the Sawyl Benuchel of the Life of St. Cadog is a displaced version of Sawyl Benisel of the North, and that the latter was situated in southern Wales because of the presence there of a St. Samuel at Llansawel.

Sawyl Benisel of the North is known to have had strong family connections in Cumbria.  See "PABO POST PRYDAIN AND HIS SONS (A MAP)" in https://mistshadows.blogspot.com/2021/07/a-fairly-radical-revision-of-my-earlier.html. What I hadn't thought about is the fact that Cunedda, in an elegy poem, is also placed in Cumbria:


This is interesting, in that Sawyl Benuchel's grave has traditional been placed on Allt Cunedda
not far from Cadog's monastery.  Cunedda in legend was said to have cleared the Irish from Kidwelly and Gower (when, in fact, he was Irish himself, hailing from Drumanagh, not Manau).  

While Cunedda's presence in the North of Britain is based upon spurious tradition, the possible association of a Sawyl with ties to Cumbria and a Cunedda who supposedly fought in Cumbria would suggest once again that the southern Sawyl is merely a relocated version of the nothern Sawyl. 

Monday, July 15, 2024

A Dumnonian or Penychen Magister Militum for Uther?: PA GUR Vs. the Galfridian Tradition

[NOTE: Since writing this piece, I have gone over the Arthurian battles again, and the connection of the name Arthur with both L. Artorius and an Irish royal family (whose lineage accounts for the Arthur name cropping up in the Dalriadan kingdom).  I've decided that the argument for an Arthur of the North is simply to strong to discount, and I cannot find a way to maintain a counter-argument for an Arthur of the South.  My book THE BATTLE-LEADER OF RIBCHESTER will stands as is.]


After over 30 years of Arthurian research, I have come to recognize two possible contenders for Uther Pendragon as those are presented to us in the traditional material.

I have recently set out my final argument for Illtud being Uther (a personage himself confused with Arthur's real father, Sawyl of the North).  But there was another one, viz. a 5th century Geraint of Dumnonia who could have taken on (or been given) the magister militum title of the British magister militum Gerontius.  Gerontius may have been called Uther because he caused dread in Sarus, or because the utriusque portion of one of his ranks had been confused in folk belief with the Welsh word uthr, spelled uter in a Latin source.  Latin utriusque has as its root the word uter. 

An Uther of Dumnonia fits in well with the Galfridian tradition, but also with some early Welsh materials, like the poem "The Stanzas of Geraint Son of Erbin." There is little difficulty fitting a Geraint as Arthur's father into the Dumonian genealogy, and all of the long-treasured Cornish, Devon and Somerset sites may be retained.  We can leave Madog and his son Eliwlad in Cornwall.  Cadbury Castle remains attractive and Glastonbury once again looms out of the mist, etc.  We even have the name Gorlois present at sites that were associated with Geraints:


But we have a problem: the Arthurian battles, if their names are taken literally, are not to be found in the South.  And they certainly aren't to be found along the border of Dumnonia and an expanding Wessex.  It is always possible, of course, that at least some of the Arthurian battle names were replaced by English ones.  In that case, as has long been recognized, we will never find them.  Still, there are definitely names that are extant in the North and it is difficult to deny their presence there.

It is also possible that during the legend-building process a purely Southern Arthur was given battles all over Britain for no other reason than to magnify his importance.  This is also a possibility scholars have recognized in the past. 

Thus the PA GUR seems to point to Sawyl Benisel, whose son could easily have fought in the Northern battles, while the tradition recorded by Geoffrey of Monmouth and other Welsh sources (which may be dependent on Geoffrey) would have us look to Gerontius/Geraint.

Which do we opt for?  How are we to decide between the two?  Is the case for the northern battles strong enough to cause us to favor a Northern Uther?  Or is the PA GUR's apparent identification of Illtud as Uther an example of spurious tradition?  

I will be addressing this issue some time in the near future.  





Saturday, July 6, 2024

Another Association of Illtud with a Sawyl

While reading up on St. Illtud's churches in Wales, I stumbled upon an interesting ancient cross carved with the names of saints, including those of Illtud and Samuel (Welsh Sawyl). The details of this cross I have pasted below.

It is thought the Samuel in question is the one of Llansawel in Carmarthenshire.[1]



RCAHMW (1976): +SAM | SON | POSUIT | HANCC[.] | UCEM+ || [--] | PROA | NMIAEI | US+
Expansion:
+SAMSON POSUIT HANC C[R]UCEM+ [ORATE] PRO ANMIA EIUS+
Translation:
Samson (PN) erected this cross...for his soul.

CAHMW (1976): +ILT[U] | [..] || SAM | SON || RE | GIS || SAM | UEL | + || EBI | SAR | +
Expansion:
+ ILT[UTI] SAMSON REGIS SAMUEL + EBISAR +
Translation:
Of Illtud (PN), of Samson (PN) the king, Samuel (PN), Ebisar (PN).




Samuel (Language: Biblical; Gender: male)
RomillyAllen/1889, 124: `The Samuel and Ebisar on the cross of Samson at Llantwit have not been identified; but the latter name is to be seen on the two crosses at Coychurch'.
Rhys/1899, 152: `Who these men were is not known...Samuel appears to have been rather common in early Wales, and in its Welsh form of Sawel it is associated with the Carmarthenshire church of Llan-Sawel'.

Anon/1928, 407: `Samuel appears to have been a not uncommon name at about the time when the cross was made'.

Nash-Williams/1950, 142: `None of the persons named in the inscription are now identifiable'.

first mentioned, 1695 Lhuyd, E.
History: The earliest references to this stone are by Lhwyd in Gibsons Camden, and in Gough's Camden (neither work consulted).
Iolo Morganwg, 1798, reproduced in Allen/1893, 326: `I have already observed that the author of the additions to Camden takes notice only of the monumental stone behind the church erected by Samson to the memory of Iltutus [this stone]. This circumstance proves that the other ancient inscribed stones [including this one] were not then to be seen'.

Rhys/1873, 9: `Aug. 30. -- The rector kindly accompanied me to Llantwit-Major, where we knew there were several inscriptions'.

Westwood/1879, 9: `This is one of the most interesting memorials of the early British Church in existence, commemorating as it does not fewer than four of the holy men, some of whose names are amongst the chief glories of the Principality. It stands in the churchyard of Llantwit, on the north side of the church...This stone was first mentioned by Edward Lhwyd in Gibson's Camden, p. 618. Strange, in the Archaeologia, vol. vi (1782), p. 22, pl. 2, fig. 1--2, gives a very insufficient engraving of it, copied in Gough's Camden, iii. p. 130, pl. 7, fig. 2. In Huebner's work (p. 22) an engraving is given of the inscription of the front of the stone in which the word `anmia' is misprinted `anima,' and with the m of the usual minuscule form'.

Allen/1889, 119: `The earliest notice of the Llantwit crosses occurs in Gibson's edition of Camden's Britannia (1695), the additions to Wales for which work were contributed by Edward Lhwyd, the Keeper of the Ashmolean Museum at Oxford. It is to this eminent antiquary, the pioneer of Welsh archaeology, that we are indebted for the first accurate knowledge of the inscribed stones. The Llantwit crosses have also been described subsequently by Mr. Strange in the Archaeologia, vol.vi (1779), by Donovan in his South Wales (1805), by Mr E Williams, otherwise known as ``Iolo Morganwg'', in the volumes published by the Welsh MSS. Society, and lastly by our old friend and associate, Prof. Westwood, in his standard work on the subject, the Lapidarium Walliae'.

Halliday/1903, 58--64, notes that the stone was eventually moved to its present position in the church in 1903. During this move, the complete outline of the cross was revealed (see form-notes). A cist grave was discovered at the foot of the cross which was considered contemporary with the cross, and as evidence that the cross had been in situ.

RCAHMW/1976, 50: `originally standing in the churchyard N. of St. Illtud's Church, and re-erected in 1903 within the W. nave of the church'.

Geology: Macalister/1949, 156: `stratified sandstone'.
Nash-Williams/1950, 142: `Local grit, apparently Carboniferous'.

RCAHMW/1976, 50: `local grit'.

Dimensions: 3.1 x 0.79 x 0.29 (RCAHMW/1976)
Setting: in ground
Location: on site
Nash-Williams/1950, 140: `All the Llantwit Major monuments are preserved in the church at the W. end of the nave'.
Form: Cramp shaft B
Iolo Morganwg, 1798, reproduced in Allen/1893, 326: `The stone inscribed to Iltutus is the shaft of an ancient cross, at the top of which the mortice still remains, into which the round stone on the top was by a tenon inserted, whereon the cross was sculptured'.
Rhys/1873, 9: `Another stone has its inscriptions separated into small compartments'.

Westwood/1879, 9: `It is an oblong block of stone about 6 feet high, its breadth below being about 29 inches, and above about 23 inches, and it is 9 1/2 inches in thickness'.

Allen/1889, 125: `The last points we have to consider are the forms of the crosses and the character of the ornament. The five sculptured monuments at Llantwit exhibit three different types; the wheel-cross, the rectangular cross-shaft, and the cylindrical pillar. The crosses of Samson, Samuel, and Ebisar, and of Houelt, the son of Res, are of the so-called wheel shape, consisting of a tapering shaft of rectangular section, surmounted by a circular head, shaped like a drum. The head of the first of these two crosses is lost, but the mortice-hole by which it was fixed on still remains; and the curve of the top enables us to conjecture that the diameter of the drum must have been about 3ft.6in. The mortice is double, the centre part being sunk 5 1/2in., leaving shoulders 2 in deep at each side (see wood cut, p. 126.). The shaft is 6ft. 6in. high, 2 ft. 7in. by 1 ft at the bottom, tapering to 1ft. 11 in. by 8 1/2 in. at the top. The bottom is left rough, showing that if was fixed in the ground without any socket stone'.

Rhys/1899, 151: `the pedestal of a cross'.

Halliday/1903, 57--58: `The Cross-shaft of Samson, commonly called the Iltyd Stone, measures 6 ft. from the gound-line upwards, and 4 ft. 2 ins. from the ground-line to the extreme base, which tapers from 12 ins. to 7 ins. in thickness (Fig. 5). The worked portion of the stone terminates in a picker-line, about 3/4 in. in breadth, a few inches below the ground line...There are no signs of either tooling or working in any form. It is simply a glacial boulder turned to account: on one side the surface is rubbed quite smooth, and shows very distinct striations'.

Macalister/1949, 156--157: `a slab...a mortice for a cross remains in the present top'.

Nash-Williams/1950, 142: `Splayed shaft (? of a composite slab-cross), formerly with extended rough butt (4 ft. long) below[2] and a rectangular shouldered mortise in the top (? for the attachment of a separate head).[3] 85" h. above butt x 30" w. and 11" t. at bottom, diminishing to 22" w. and 10" t. at top...The shaft is decorated on all faces with carved patterns in low to medium relief (extensively damaged by flaking), and is also inscribed...The stylistic relationship of this monument to Nos. 159, 303, and 360 has already been noted (p. 116).

[2] See AC, 1903, [Halliday/1903] p. 58 (figured).

[3] For the probable form of the head see p. 115, note 3'.

RCAHMW/1976, 50--51: `Shaft of composite cross, probably disc-headed...The exposed part of the stone...with well-squared angles and splayed faces, stands 2.15m high, the total length with the buried lower part being 3.10m. The main faces taper upwards from 79cm to 58cm in width, and the thickness decreases from 29cm to 24cm. It has carved decoration on all faces, varyingly weathered, and both main faces carry inscriptions.

In the top of the shaft a rectangular mortice has been cut 11.4cm deep, countersunk with wide shoulders 6.4 cm deep, for a separate cross-head now lacking. This most probably took the form of a disc-head, for which there is some evidence in the deliberate concavity of the upper surface[1] and in that the decorative patterns on the narrow sides need to be completed by being continued on the sides of a head of similar width (cf. No. 911). Its size may be estimated by comparison with Nos. 903, 907 and 911 rather than from the degree of curvature of the surviving top surface...The form of the shaft and in particular its decorative patterns are very similar to those on the `Cross of Eiudon' (E.C.M.W. 159), and the two stones may have been carved by the same hand'.

Condition: complete , some
Westwood/1879, 9--10: `The front face has unfortunately been much injured by the scaling off of large portions, nearly the upper half and a portion of the lower division having thus been lost, caused by the climbing of children up the stone. We can only conjecture that the upper part may have contained a cruciform design, or that it may have been surmounted by a wheel cross'.
Macalister/1949, 157: `the surface is, however, badly scaled'.

Folklore: none
Crosses: none
Decorations: 
Westwood/1879, 10: `Sufficient remains of the upper part of the lower division of the face of the stone to show that it was ornamented with the curious Chinese-like design (with small raised bosses in the open spaces), of which the complete pattern may he seen upon the cross at Neverne and on that of Eiudon.

The back face of the stone (Pl. IV) is more complete than the front, although both the broad interlaced ribbon designs in the upper part have been injured by exposure to the weather; the lower part is filled by a large design of straight interlaced ribbons like basket-work...The two small compartments at the sides of this inscription [second part of LTWIT/2/2] are filled with the double interlaced oval pattern, which is also used along the upper part of one of the edges of the stone (Pl. III), below which is the well-known pattern formed of four T's, with the bottom of the upright strokes directed to the centre of the pattern. The other edge of the stone has thirteen squares filled with a diagonal and square design'.

Allen/1889, 125--126: `The ornament on the Llantwit stones consists of interlaced and key-patterns arranged in panels of the same class as that found in the Irish MSS. of the ninth and tenth centuries. There is none of the spiral decoration which is characteristic of the earlier MSS., sculptured crosses, and ecclesiastical metal work.

Attention should be particularly directed to three peculiar patterns on the crosses of Samson, Samuel, and Ebisar, -- (1), two oval rings interlaced crosswise; (2), four T's placed in the shape of a fylfot or swastica; and (3) a simple key pattern. Similar designs occur on three other crosses in Wales --- at Golden Grove, Caermarthenshire; and at Nevern and Carew, Pembrokeshire'.

Macalister/1949, 157: `The devices were chisel-cut, and so far as they remain are in good condition... For the details of the ornament, see the illustrations'.

Nash-Williams/1950, 142: `Front. The decoration is disposed vertically in panels: (a) diaper key-pattern (?) (vestiges only); (b) double horizontal panel containing parts of a Latin inscription in five and three lines respectively, reading horizontally (see (1) and (2) below), with a four-lobed plain twist (R.A. 501) in the field below the second inscription; (c) four squares of diaper key-pattern (cf. R.A. 1010 and 1012),[4] with pellets symmetrically disposed in the interspaces. Right. Vertical band of fourteen squares of diaper key-pattern variously disposed (R.A. 99, a characteristic S. Wales motif). Back. Panelled decoration as before: (a) remains of twelve-cord double-beaded plaitwork, with irregular vertical and horizontal breaks; (b) double horizontal panel with a Latin inscription in two parts, each of two lines reading horizontally (see (3) and (4) below); (c) twelve-cord double-beaded plait with irregular breaks (as before); (d) quadruple horizontal panel, the inner compartments containing parts of an inscription each in three lines reading horizontally (see (5) and (6) below), the two outer pairs of interlinked oval rings (R.A. 766); (e) coarse sixteen-cord plain ribbon-plait, with one break. Left. Narrow vertical panel filled with seven pairs of interlinked oval rings (R.A. 766) above and three squares of swastika key-pattern (R.A. 921) below.

[4] The pattern is apparently peculiar to S. Wales'.

RCAHMW/1976, 50: `On the E. face (as when in situ and as now re-set) the decoration forms three main panels in vertical order within plain continuous angle-mouldings. The uppermost panel has almost entirely flaked away, leaving weathered traces of diagonal swastika key-patterns probably arranged in six squares. A shorter panel below, framed and divided vertically by plain beading but not sunken, contains two horizontal inscriptions...The lower part of the right-hand panel is cut back to leave in relief a four-lobed plain twist. The lowest main panel, partly defaced, is formed of four squares of diagonal swastika key-pattern with paired pellets in all the outer segments.

The narrow S. side of the shaft forms one vertical panel, its upper two-thirds containing seven knots of double-beaded intertwining oval loops, the remainder filled with three squares of swastika key-patterns.

The W. face has three main panels of carved ornament separated by two bands of demi-panels with inscriptions. The damaged topmost panel contains irregular double-beaded plaitwork incomplete in itself and formerly continued on the missing cross-head. A plain horizontal beading separates this from a pair of rectangular demi-panels below, each framed by similar beading but not sunken...The central main panel is a square containing ten-cord double-beaded loose plaitwork with unsymmetrical breaks. Below it in a horizontal row are four equal rectangular demi-panels, the two outer ones each filled with a knot of double-beaded intertwined oval loops. The inner demi-panels, framed by plain beading but not sunken, have inscriptions...The lower half of the face forms one large panel filled with regular plain sixteen-cord plait, in which there is one break at the top.

The narrow N. side forms one vertical panel filled with fourteen squares of diagonal key-pattern alternating in direction except that the five upper squares are identical. The top square is incomplete, suggesting that the pattern was continued on the head'.

[1]

While the following is true (passage from The Lives of the British Saints: The Saints of Wales and Cornwall and Such Irish Saints as Have Dedications in Britain, Volume 2, Sabine Baring-Gould, John Fisher, For the honourable Society of cymmrodorion, by C. J. Clark, 1908) -

"The genealogies of the Welsh saints give his [St. Asaph's] father's name as Sawyl Benuchel, the son of Pabo Post Prydain, but in the very early genealogies in Harleian MS. 3859 he appears as "Samuil pennisel map Pappo post priten," with epithet 'Penisel" (of the low head) or "Penuchel" (of the high head).  The later genealogists confounded him with the Glamorganshire chieftain (dux), Sawyl Benuchel..."

- it also appears the St. Sawel of Llansawel in Carmarthanshire was confused with Sawyl of the North.
I say this because Llansawel is on the Afon Marlais.  The southern Llangadog is by Allt Cunedda, where Sawyl Benuchel was supposedly swallowed up by the earth, but the northern Llangadog is very near another Afon Marlais.  See the maps below.  Thus it is likely that it was St. Sawyl, possibly the Samuel of the Illtud Cross, who was confused with Sawyl of the North.  In other words, there never was a separate southern dux named Sawyl who came to figure in the Life of St. Cadog. 

All of this is important because in the Life of St. Cadog it is the 'dux' Sawyl Benuchel who, with his men, commands the food and drink raid on the saint's monastery. In the Life of Illtud, it is the men of the war-chief Illtud who commit this crime.  

Llansawel and the Afon Marlais 1

Llangadog North and the Afon Marlais2

Llangadog South and Allt Cunedda









Wednesday, July 3, 2024

A STARTLING DISCOVERY BRINGS BACK THE SAWYL-UTHER IDENTIFICATION


I had only just decided on "keeping" the Northern battles for Arthur, but in dispensing with Sawyl Benisel as Uther.  See my logic behind this conclusion here:


But before I put away Arthur forever, I decided to check over one more thing that continued to bother me: why does the name Arthur first appear in the royal line of the Irish-founded kingdom of Dalriada, and then later in the Irish-founded kingdom of Dyfed?  When I had proposed Sawyl as Arthur's father, the problem went away, as Sawyl had married a daughter of Muiredach Muinderg of the Dal Fiatach.

So, I combed through what is known about the British connections of Aedan of Dalriada, purportedly the father of an Arthur.  While re-reading Bannerman (STUDIES IN THE HISTORY OF DALRIADA), I chanced to bother to consult the footnotes.  The text on p. 89 read:

"... it is said that [Maith] Gemma [from Irish mathgamain, 'a bear'], the saint's mother, was a daughter of Aedan and a niece of a British king which implies that Aedan's wife was of British extraction."

And the footnote:

"This is probably the Maithgemm of Monad [the Dalriadan capital], daughter of Aedan... It seems she married a certain Cairell, grandson of Muredach Munderg, of the Dal Fiatach."

What this means (for those who don't see it immediately!), is that Muiredach marries a daughter to Sawyl Benisel, and then, later, a grandson to Aedan's daughter. A son Arthur of Sawyl and the Irish princess would be roughly contemporary with Gemma and Cairell.  The Dalriadan Arthur would have been named after the famous British one via obvious family connection.  

I will note that there is a problem in the Irish sources regarding the Dalriadan Arthur's father.  He is called both Conaing (an Irish version of the English word cyning, 'king') and Aedan, with Conaing being said to be a son of Aedan.  Bannerman discusses this conflict as follows:

"There remains the problem of whether Artur was Adan's son or grandson.  The combined evidence of Adomnan and AT is strong.  However, it should be remembered that the original compilation of the Senchus, if it is to be accepted as an historically authenticated document, should be dated to c. 650, some fifty years earlier than Adomnan or the Scottish annals underlying AT.  Furthermore, Aedan was in his seventies when he died and it would be strange indeed, considering that he had seven sons, if, towards the end of his life, none of his grandsons was of an age to take a part in the political activities of his time.  Artur, grandson of Aedan, might easily have been twenty years of age, or more, by 590. It is at least possible that Adamnan and the compiler of the Iona Chronicles, when referring to those of Aedan's descendents who died before him, assumed that they were all his sons, especially as some were so in fact." 

Allowing, for the sake of argument, Conaing as the Dalriadan Arthur's father, we can draw out the following comparative genealogies for the two Arthurs:

Sawyl-Dechtire, d. of Muiredach                                

                     Arthur                          Conaing        Gemma-Cairell, gs. of Muiredach

                                                            Artur        

To me, this is incredibly convincing.  And, indeed, it provides the one piece of real evidence I was missing that would allow me to feel confident about Sawyl as Uther.