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Ifor Bach, Lord of Senghenydd
Ancestors and Children of the Lord Rhys

                               THE LEGENDARY KINGDOM OF SEISYLLWG
                                               By Darrell Wolcott
         The noted Welsh historian, J.E. Lloyd, when speaking of Ceredigion, asserts "Seisyllt, who was king about 730, embarked on a career of conquest and added to Ceredigion the three cantrefs of Ystrad Tywy, the whole dominion being henceforth known from the name of its founder as Seisyllwg".[1]  Undoubtedly, Lloyd is referring to the Seisyllt ap Clydog descended from Ceredig ap Cunedda who is cited in Harleian Ms 3859 as an ancestor of Gwgan ap Meurig.
        A look at the sources Lloyd used to support his statement shows it to be more legendary than real.  First, he offers a line from the Mabinogion tale "Pwyll Lord of Dyfed" which reads "Pryderi (son of Pwyll) ruled the seven cantrefs of Dyfed prosperously, beloved by his country and by all around him; moreover he conquered the three cantrefs of Ystrad Tywy and the four cantrefs of Ceredigion, and these are now called the seven cantrefs of Seisyllwg."[2]  Never meant to be historical, that tale would date the creation of Seisyllwg to the late 6th century.  It claims Pryderi married a daughter of Gwyn ap Gloyw ap Casnar[3], an historical man born c. 540, so Pryderi is placed about c. 560.  No explanation is offered for naming the new kingdom "Seisyllwg".
        Next, Professor Lloyd cites the writing of two 19th century men: Basil Jones, author of "Vestages of the Gael in Gwynedd", and Egerton Phillimore, editor of the magazine "Y Cymmrodor".  The latter, in vol xi, was speaking of Cantref Mawr in Ystrad Tywy when he says "In the early times this cantref belonged to Demetia, or Dyfed, but it was conquered in the 8th century, with two other cantrefi south of the Towy by or before the time of Seissyll ap Clydog, king of Ceredigion, from whom the district of Ystrad Tywy, comprising the said three cantrefi, was called, together with Ceredigion, Seissyllwg or Seissyll's land".[4]  Phillimore cites the Pwyll tale in the Mabinogian as his authority for the statement.  So he would have it that a king of Ceredigion took Ystrad Tywy from Dyfed, while the Mabinogion story claims the opposite happened...and the two versions of the creation of Seisyllwg are separated by two centuries. 
          The next authority given by Professor Lloyd is Vol 2 of Aneurin Owens' "Ancient Laws and Institutes of Wales", pp 50.  This passage retells the mythical story of how Maelgwn used a chair composed of waxed wings to remain afloat while men representing the other kingdoms in Wales all sank when the tide came in, allowing Maelgwn to prove his entitlement to be supreme king.  Among the lesser kings who were bested by his trickery was one representing Seisyllwg.  Again, that tale is not historical but claims there was a kingdom called Seisyllwg as early as c. 525 when Maelgwn came to power. 
          The final "source" cited by Lloyd is Triad 14 in series iii.[5] The Series iii triads were composed by Iolo Morgannwg (obit 1868) and were not considered authentic ancient material by Rachel Bromwich when she published her scholarly work "Trioedd Ynys Prydein".  The fact that Iolo mentioned lands called Seisyllwg is entitled to no weight in our search for historical truth; his other writings show no inclination to stay with the facts.
          Thus, we find little in the literature beyond the borrowing from a Mabinogion tale and changing the era to suit the new tale being related.  Phillimore and Lloyd date the formation of Seisyllwg to correspond with the estimated reign of an 8th century Ceredigion king named Seisyllt even though two other tales say it existed 200 years earlier.  When viewed alongside other "kingdoms" named in the Mabinogion[6], it ceases to belong to history so much as to legend. 
        If such a consolidation of Ceredigion and Ystrad Tywy ever took place, it must have dissolved before the year 900; the Brut entry of 872 calls Gwgan ap Meurig "king of Ceredigion", indicating those lands had their own king independent of Ystrad Tywy.  Further, the entry of 807 citing the death of Arthen (ap Seisyllt) calls him "king of Ceredigion" and this was within one generation of the man who supposedly created Seisyllwg. 
         One might logically ask, what difference does it make whether or not there was a kingdom of Seisyllwg in the 9th century?  It is crucial to the claim that Rhodri Mawr "inherited" it from his reputed wife, Angharad ferch Meurig, sister of king Gwgan ap Meurig.  Those who make that claim could not simply say she was the heiress of Ceredigion; Rhodri's supposed seat for that part of his empire was Dinefwr located in Ystrad Tywy, not Ceredigion.  It is certainly beginning to look like his "rule" in that part of Wales is as bogus as we have shown his rule in Powys to have been.  While various medieval and modern writers assert, as though it were established history, that Cadell ap Rhodri Mawr inherited a vast kingdom in south Wales, no ancient sources confirm that notion.  Professor Lloyd only calls it "most probable" and based on the fact that his descendants are found in south Wales.  But those were also descendants of Cadell's son, Hywel Dda, who did in fact rule from Dinefwr in Ystrad Tywy.  And it was no inheritance from either his father or his grandmother.
         Perhaps we should begin at the inception of this new dynasty, with Merfyn Frych.  As the maternal grandson of the last male descended from the First Gwyedd Dynasty (his mother was Esyllt ferch Cynan Dindaethwy, an only child), Merfyn came to Anglesey from the Isle of Man in 816.  He forcefully ousted Hywel ap Caradog from the island cantref and sent him back to his patrimony of Rhos. One would suspect his first order of business was to meet with the heads of other families who had recognized Cynan Dindaethwy as their king.  After securing their support for his kingship claim, as much by sword-rattling as by any entitlement via his mother, he would have likely turned his attention to the kingdom of Meirionydd, still ruled by descendents of Meirion ap Cunedda.  Its king was Cynan ap Brochwel ap Ednyfed.  We suspect Merfyn Frych was able to bring those lands into his sphere of influence by agreeing to marry a daughter of Cynan.  He was then about 29 years old and unmarried.  We suggest it was Nest ferch Cynan ap Brochwel of Meirionydd whom he married, not the mythical "Nest ferch Cadell ap Brochwel of Powys".[7]  But that Nest was no heiress (Cynan had a son, Cadwaladr) and she brought no land to her husband or their sons. 
         When Merfyn died, or was killed, in 844, his son Rhodri was perhaps 24/26 years old.  It is possible that Merfyn's brother Cadrod acted as interim king until Rhodri attained "full age", but he might have immediately succeeded his father if born as early as 716.  This was the era of invasions by both Vikings and Saxons, and Rhodri set out to unite the Welsh Cymry for self-defense.  He found both Caradog Freich Fras ap Hywel of Rhos and Brochwel ap Aeddan of Powys eager to pool their forces to resist the Saxons who, unlike the Viking sea raiders, sought Welsh lands and not simply lootable valuables.  But the kingdom to his south, Ceredigion, may have been reluctant to lend its warband to the united army proposed by Rhodri.  Its king, Meurig ap Dyfnwal, was directly descended from Ceredig ap Cunedda and his family had fended off for centuries any overtures to fall under the influence of Gwynedd.  Assuring Meurig that his lands would remain as an independent kingdom, Rhodri Mawr likely secured a military alliance with Ceredigion by marrying Meurig's daughter Angharad.[8]  Again, this marriage brought no lands with it; Meurig had a son, Gwgan.
        Medieval writers claim this marriage was to bring the kingdom of Seisyllwg to Rhodri, when King Gwgan ap Meurig died in 872 without heirs.  Not only is it doubtful there ever was a kingdom of Seisyllwg, we suspect that Einion ap Meurig ap Caradog ap Cloddien Frych ap Llowarch ap Seisyll ap Eiddon Ddu[9] of a cousin line of Gwgan ap Meurig was a logical member of the Ceredigion Dynasty to inherit its rule.  But Angharad may well have inherited the personal manor of her brother and father, and it may have been a part of the inheritance of her son Cadell.  But whatever lands those may have been, they were in Ceredigion and not near Dinefwr.
          By Angharad ferch Meurig, Rhodri had at least 3 sons who survived him when he was killed in 878.  Anarawd, the eldest, succeeded him as king of Gwynedd, while Merfyn ap Rhodri was given the lordship of Lleyn and probably the neighboring cantrefi of Eifionydd and Ardudwy.  While the third son, Cadell, would have inherited scattered manors throughout those lands now ruled by his brothers, if he held any lordship at all we do not know where.  Nor do we have any early authority which cites his marriage; modern writers call her Rheingar but give her no ancestry. By tradition, she supposedly was a lady of Dinefwr in Ystrad Tywy.
         Subsequent events lead us to identify this lady as probably a sister of Llywarch and Rhodri ap Hyfaidd ap Bledri; that family had replaced the ruling Dyfed family when it became extinct in the male line.  Owain ap Maredudd ap Tewdos (descended from the ancient Deisi dynasty of Dyfed) had only a daughter, Tangwystl:
                                650  Cadwgan ap Caten
                       l                                                      l
           680  Rhain                                       685  Tryffin[10]
              (king of Dyfed)                         (lord of Ystrad Tywi)
                       l                                                      l
          710  Tewdos                                      715  Cynan   
        740  Maredudd                           To Cadifor Fawr of c. 1030
         775  Owain                           
        (king of Dyfed)                 
      810  Tangwystl                   
     (heiress of Dyfed)       
         Tangwystl, the heiress of Dyfed, married an unidentified man called Bledri.  According to the Triads, this man was not a nobleman of Wales.[11]  We prefer to think he was described in that manner simply because no pedigree could be found citing his ancestry.  It is inconceivable that the heiress to a major Welsh kingdom would be given in marriage to a nobody. 
      Tangwystl's father, Owain ap Maredudd, had become the interim king of Dyfed when his older brother, Rhain, died in 808. A third brother, Iddon, probably died young. [12]  Rhain was survived by a son, Tryffin, but the boy was barely 13 years old.  We suggest that Owain also had a sister [13] who was married to Dyfnwallon ap Arthgen, king of Ceredigion, and had two sons, the youngest named Bledri. [14]  If so, then Bledri and Tangwystl were first-cousins. 
         The Royal Family of Dyfed, in 810, consisted of a single adult male (Owain) plus one male child (Tryffin) and one female child (Tangwystl).  Persons who were only maternally related to the family included Owain's brother-in-law, Dyfnwallon, and his two male children, Meurig and Bledri:
                   740  Maredudd ap Tewdos ob 796
             l                            l                  l                   l
768  Rhain, ob 808   775  Owain   780  Iddon    785  Dau=====Dyfnwallon  770 
             l                             l             d.s.p.                    l        l
 795  Tryffin           810  Tangwystl     < 800       802  Bledri  Meurig  800 
       The Brut records the death in 811 of an Owain ap Maredudd, not otherwise identified. If this was the king of Dyfed, then the Dyfed kingship must have been conferred upon Dyfnwallon as the only living adult.  If the man in the obit was some other Owain ap Maredudd, [15] then Dyfed's King Owain didn't face a succession crisis until 814.  His nephew, Tryffin ap Rhain, died that year, as a young man not yet age 20.
        We can't be sure if it was Owain or Dyfnwallon who was king of Dyfed in 828 when Tangwystl was given in marriage to Bledri, [16]  and do not know whether Bledri ever became king himself or if his son, Hyfaidd, was the first king in the new Royal Family. [17] If our chart is correct, Bledri would have a claim to kingship even had he not married Tangwystl; he was a maternal grandson of former king Maredudd ap Tewdos. [18]
           We can now chart the marriage connections which the clan of Rhodri Mawr made with the Ceredigion and Dyfed families:
                   790  Merfyn Frych     800  Meurig
                                   l                         l
   2nd wife===== Rhodri Mawr====Angharad  835
                     l                      820   l                    Hyfaidd  830
                     l                              l               ______l_______
                     l                              l               l                       l 860
        865  Tudwal             851  Cadell===Rheingar 866   Llywarch
                   =                                     l                                l 895
 Elen f. Aleth ap Bledri            879  Hywel Dda=========Elen
        Asser's Life of King Alfred says that the sons of Rhodri Mawr were threatening Hyfaidd's lands so that king submitted to the overlordship of Alfred for protection.[19]  Perhaps it was Alfred's idea that two sons of Rhodri Mawr should marry granddaughters of Bledri, the first-cousins Rheingar ferch Hyfaidd and Elen ferch Aleth.  This was a common tactic which allowed sons of potential conquerors to obtain lands by marriage rather than by combat.  
       It would appear that land is all that Tudwal ap Rhodri[20] obtained in Dyfed, and Tudwal (being lame) expected nothing more.  But Cadell wanted a kingdom the equal of Gwynedd which his elder brother Anarawd ruled.  Standing in his way were his brothers-in-law Llywarch and Rhodri ap Hyfaidd.  It is unknown how Llywarch, who became king of Dyfed in 893, met his death in 904 but his brother Rhodri must have then claimed the kingship.  
       The Annales Cambriae tell us in 904 that "Rhodri ap Hyfaidd's head was struck off".[21]  That language seems to imply an execution, not merely death on the battlefield.  If he continued the assault on the church of David which Asser says marked the reign of Hyfaidd his father, it may have given Cadell the opportunity to seek his arrest and execution.  But Cadell was now about 55 years old and perhaps in poor health....he died a mere 5 years later.  His sons Hywel and Clydog, however, were in their mid-20's; almost immediately after the last male heir of Dyfed was executed, Hywel Dda ap Cadell married the young daughter of Llywarch ap Hyfaidd.  And this, we believe, was when the clan of Rhodri Mawr first obtained the manor at Dinefwr.  Hywel quickly cowed the other dynastic families of Ceredigion and Dyfed into accepting local lordships subject to him as king, calling the combined kingdoms (Dyfed and Ceredigion) by the new name "Deheubarth".  Initially, Hywel may have ruled with one or more of his brothers, but in 921 he did homage to King Edward the Elder and can be assumed to have been in sole control of Deheubarth after the death of Clydog.[22]
         Our view, accordingly, is that "Seisyllwg" or "Seisyll's lands" was no more than Ceredigion; that Dyfed comprised most of what is now called Pembrokeshire and Carmarthenshire, and that Deheubarth was formed by Hywel Dda by combining the two kingdoms.  Moreover, we believe none of it was ever held by Rhodri Mawr; if Cadell ap Rhodri ever ruled anything from Dinefwr, it was only between 905 and 910.

[1] J.E. Lloyd "A History of Wales from the Earliest Times to the Edwardian Conquest", 2nd edition, 1912, p. 257
[2] Jeffret Gantz, translation "The Mabinogion", 1976, p. 65.  The oldest extant manuscript containing fragments of the Pwyll tale is Peniarth 6 written c. 1225.  How much earlier the tale may have circulated orally is not known, but probably not much earlier than the 11th century.
[3] Pen. 128, 66 calls him "Gwynn gohoyw ap Gloyw gwlad lydan ap Llarf ap Kassnar wldeic"; our reconstruction of the timeline for this family suggests that the Mabinogion tale errs in omitting "Llara" as the father of Gloyw.  Extant sources refer to the family patriarch as both "Casnar Wledig" and "Cassanauth Wledig"
[4] Y Cymmrodor, 1892, vol xi, p. 56
[5] "Myvyrian Archaiology of Wales", 1870, p. 402
[6] In the Pwyll tale, a prominent figure is Arawn, king of Annwvyn, whose realm is said to border Dyfed.  No such real kingdom is known to have ever existed and many consider it to be the Other World of Welsh mythology which "lies so far west of Wales that one cannot reach it unless you are dead".
[7] See the paper "Nest ferch Cadell ap Brochwel" which suggests no such 9th century lady existed, at the link below:
[8] The marriage of Rhodri Mawr to Angharad ferch Meurig of Ceredigion is cited in ABT 6j and Jesus Coll. Ms 20, items 20, 21 and 42 
[9] Pen. 140, pp 348/349 and Mostyn Ms 212b, pp 91/92 make Eiddon Ddu a son of Ceredig ap Cunedda, but the timeline of his descendants point to c. 635 for his birth.  We suspect he was a brother of Arthglwys ap Arthfoddw, the paternal ancestor of Meurig ap Dyfnwallon.  That line failed in the late 10th century with Odwin ap Teithwalch, whose only daughter married Eunydd ap Pyll of Meirionydd and carried Castell Odwin to her son. 
[10] ABT 18b says "Triffyn ap Owain vraisc".  That Tryffin was the father of Aircol Lawhir of the 5th century, but the Tryffin who was the father of Cynan in the pedigree of Cadifor Fawr would date to c. 680 and was probably a brother of Rhain ap Cadwgan.
[11] Triad 68 names "Hyfaidd ap Bledri of Deheubarth" as one of 3 kings who sprang from villeins, i.e. the lower class of non-free men who were bound to the land.  Deheubarth simply refers to the "right-hand side of Wales"; early maps were oriented with East on the top, so South was on the right.  Harl, 3859, 2 cites a "Hyfaidd son of Tangwystl ferch Owain ap Maredudd" in the line of kings of Dyfed.  Thus Tangwystl was the wife of Hyfaidd's unnamed father.  Most would identify him with the king in the cited triad.
[12] While Iddon is cited in Harl 3859, 14 as a brother of Rhain and Owain ap Maredudd, he is never again mentioned in any extant source, primary or secondary.  It seems clear that he was never involved in the subsequent Dyfed kingly succession
[13] No known sources say Owain ap Maredudd had a sister, this is simply our suggestion to explain the probable origin of the Bledri who fathered Hyfaidd and was married to Tangwystl ferch Owain as cited in Harl 3759, 2 and ABT 18a
[14] No sources identify the wife of Dyfnwallon nor the father of Bledri 
[15] We believe there was a Owain ap Maredudd ap Tewdos ap Cadwgan in the Dyfed family, a brother of Ceingar ferch Maredudd cited in JC 20, 12   Such an Owain would have been near age 65 in 811, while King Owain ap Maredudd would have only been about age 36 that year.
[16] If it was not King Owain ap Maredudd who died in 811, the birth of Tangwystl might have been near 815, making her only 14 when she married, the typical age for a young lady to marry in that society   
[17] Hyfaidd was not old enough to become king prior to c. 858 and it is doubtful either Owain ap Maredudd or Dyfnwallon could have lived until then.  Either Bledri or his brother must have served at least briefly as king of Dyfed as there were no other eligible candidate
[18] But so was his older brother, Meurig, who might have served briefly as king of both Ceredigion and Dyfed, awaiting Hyfaidd to reach kingship age.
[19] Translation by Simon Keynes and Michael Lapidge published by Penguin Books in 1983, pp 94-96
[20] Burke's Commoners, vol iv, pp 381 says "Tudwal espoused Helen, daughter of Aleth who, in the genealogies, is styled brenin Dyfed".  It was Hyfaidd who was king of Dyfed at the time Tudwal Gloff would have sought a wife, and we believe Aleth was a younger brother of that king.  The male name "Aleth" occurs often among families descended from Tudwal and is unknown in other families.  Tudwal's lands were in Rhufoniog in Gwynedd but two early families said to descend from him are found in Dyfed, suggesting he did marry a lady from south Wales.  He was only a half-brother of Cadell and about a half-generation younger.
[21] The date is emended to 905 in the Brut, two versions of which render his name corruptly as "Rhydderch" ap Hyfaidd
[22] The Anglo-Saxon Chronicle entry for 921 names three Welsh kings who gave allegiance to King Edward as "Hywel, Clydog and Idwal".  However, the Brut says the Clydog who was Hywel's brother was killed in 920.  One of these dates must be off by a year or so as no other Clydog is known to have been a Welsh king in that era.