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". 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." 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, 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". 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. 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, 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
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 Tyndaethwy, 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 Tyndaethwy
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". 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. This was the era of
invasions by both Vikings and Saxons, and Rhodri set out to unite the Welsh Cymri 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. 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 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
(king of Dyfed)
(lord of Ystrad Tywi)
To Cadifor Fawr of c. 1030
(king of Dyfed)
(heiress of Dyfed)
the heiress of Dyfed, married an unidentified man called Bledri. According to the Triads, this man was not a nobleman
of Wales. 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
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.  Rhain was survived by a son, Tryffin, but the boy was barely 13 years
old. We suggest that Owain also had a sister  who was married to Dyfnwallon ap Arthgen, king of Ceredigion, and
had two sons, the youngest named Bledri.  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
ob 808 775 Owain 780 Iddon 785 Dau=====Dyfnwallon 770
l l d.s.p.
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,  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,  and do not know whether Bledri ever became king himself or if his son, Hyfaidd, was the
first king in the new Royal Family.  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. 
can now chart the marriage connections which the clan of Rhodri Mawr made with the Ceredigion and Dyfed families:
790 Merfyn Frych 800 Meurig
2nd wife===== Rhodri Mawr====Angharad 835
l 820 l
852 Cadell===Rheingar 866 Llywarch
Elen f. Aleth ap Bleddri 880
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. 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 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". 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.
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.
 J.E. Lloyd "A History of Wales from the Earliest Times to the Edwardian Conquest",
2nd edition, 1912, p. 257
 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.
 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"
 Y Cymmrodor, 1892, vol xi, p. 56
 "Myvyrian Archaiology of Wales", 1870, p. 402
 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".
 See the paper "Nest ferch Cadell ap Brochwel" which suggests no such 9th
century lady existed, at the link below:
 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
 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.
 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.
 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.
 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
No known sources say Owain ap Maredudd had a sister, this is simply our suggestion to explain the probable origin of the Bleddri
who fathered Hyfaidd and was married to Tangwystl ferch Owain as cited in Harl 3759, 2 and ABT 18a
No sources identify the wife of Dyfnwallon nor the father of Bledri
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.
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
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
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.
 Translation by Simon Keynes and Michael Lapidge published by Penguin Books
in 1983, pp 94-96
 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.
 The date is emended to 905 in the Brut, two versions of which render his
name corruptly as "Rhydderch" ap Hyfaidd
 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.