LANDS CALLED GARTHMADRYN
We speak here of those lands which lay north of Morgannwg, east of Ystrad Tywy and south of Powys,
comprised mostly of the Black Mountains, which later took the name Brycheiniog. We hesitate to call Garthmadryn a "kingdom"
since we do not know that its regulus was truly independent of the kingdoms it bordered. Nor do we know the era in which
it was first given a name. Its recorded history mostly begins c. 300 AD and ends with the rise of Brychan c. 400.
What we do find in the early literature is a mythical tale  set in the 1st century AD which
claims that a Goth soldier from Greece somehow charmed himself into a favorable marriage with the daughter and sole heiress
of the "regulus" of Garthmadryn. That regulus was named Gwraldeg, his daughter was Morfydd and the dashing Goth was
called Teithall or Tathall. When we analyze the family said to result from this marriage, all known factors point to
a date nearer 290 AD for the birth of the son of Teithall, who was named Teithin..
No part of that tale is mentioned in the oldest Brychan manuscript, "De Situ Brecheniauc" ,
thought to have been written in the 11th century. Instead, we find a pedigree of Brychan which includes no marriage
matches prior to that of Brychan's parents. Standing atop that pedigree is a "Teudfal filius Annhun, rex Grecorum".
A later manuscript, "Cognatio Brychan" , seems to have drawn from the same original source as De Situ, but renders that
original patriarch as "Tathal filius Annun nigri, regis Grecorum". Both of these manuscripts say that the territory
was, before the era of Brychan, known as "Garthmatrun" or "Garthmathrim" but say nothing of its history or it rulers.
Both then and during the 11th century, the southeast corner of Garthmadryn/Brycheiniog known
as Ystrad Yw was a part of the kingdom of Gwent, which bordered it to the south. After being included in the English Breconshire,
the ancient Ystrad Yw formed most of the hundred called Crickhowell.
Brychan's pedigree, with our estimated dating and preferred spelling, is given as:
260 Teithall, son of Annun Ddu of
385 Marchel=======Anlach ap Cormac,
an Irish "king"
One might reasonably assume this family of Goths (not Celts) sprang from an officer in the
Roman army who was stationed in Brition and who, when he completed his term of service to Rome, elected to remain in Briton.
He had probably made friends with whatever family ruled Garthmadryn and was made welcome to settle there, perhaps even given
a local lady as his wife. Alternately, he might have been assigned as the local military ruler of the area, and remained
there as a civilian war lord after his discharge from the Roman military. History has always been written by the winners
and no Garthmadryn family except his is known during the era 290-400.
The early Brychan manuscripts mentioned above relate a tale to explain how the daughter of a Goth
king in Garthmadryn was married to an Irishman. It involved the king taking his daughter overland to the Irish Sea, sailing
across to be met by a king in Ireland who was smitten by the daughter and married her. She remained in Ireland until
she bore a child who they named Brychan, then the family moved to Garthmadryn.
Perhaps it did happen that way, but we suggest there were lots of Irishmen right next door to
Garthmadryn…..the Deisi tribe which had come to Wales about the year 342. The father of Brychan, Anlach ap Cormac
, was about the same age as Aeda Brosc of the Deisi , and may have represented a branch of the tribe who settled further
east in Wales than others who remained in Dyfed.
The story of Garthmadryn ends here. When Brychan grew up and became the new ruler of the
territory, it was renamed "Brychan's land" or "Brycheiniog" (which the English pronounced Brecknock).
 This tale is related in Theophilus Jones' "History
of Brecknock", Glanusk Edition, Vol 1, page 29
 Both the original Latin version, and an
English translation, are printed in Y Cymmrodor, vol XIX (1906) pp 24-34
 An English translation of this manuscript
is printed in the same issue of Y Cymmrodor mentioned in Note 2, pp 35-37
 A pedigree of Anlach, back to an Irishman
named Briscethach, is cited in Vita Cadoci #46, but omits the father of Anlach. That name is supplied by shorter pedigrees
in Di Situ Brecheniauc and Cognatio Brychan. There is nothing in his pedigree which connects him to the Deisi tribe,
if he in fact was a Deisi.
 For the early
pedigree of the Deisi in Wales, see our paper "Maxen Wledig and the Welsh Genealogies" at the link below: