So, there was this Brythonic kingdom in what's now England called Pengwern. Cambrian Chronicles has a good videö about it. It's mentioned in like three places. It's capital is disputed. Some say it's actually just Shrewsbury in Welsh, but that's Amwythig, a name which we can't figure out what it means and so is probably very old with contextual sound changes blurring wherever the words that make it up used to join to the point we can't tell where it is.
One of the sources is Canu Heledd. This is a poëm written in the voice of but not by Heledd ferch Cyndrwyn, a princess, and sister of Cynddylan, the last king of it.
So anyway, one of the places mentioned is Tren and aa lot of people think it's the river Tern, but according to the translation I linked above that doesn't sound quite right. The poëm says "Protected Tren, the town of his father!", and "Defending Tren, that wasted town!", ah yes, because "That wasted town" is a reference to a river.
Google maps has a town called Tern on the river but nowhere else does so that's probably an example of what they call a paper town. I'm just gonna say Tren is probably some now lost Welsh name for somewhere in England. (I couldn't find any possible Latin matches in Britain for Tren either, no Trandium, or anything).
Actually, Tren does also seem to be a river as there is a segment of the poem that goes "Parallel with the Avaerwy,/The Tren enters the Trydonwy,/And the Twrch falls into the Marchnwy./Parallel with the Elwydden, /The Trydonwy flows into the Tren, /And the Geirw flows into the Alwen."
Unfortunately I cannot find much about this River Trydonwy. The Twrch is a river far to the west of Pengwern, which we know thanks to the lines about the Church of Basa.
The poem also in a section lamenting the fate of Cynddylan's hall. This is called Stafell Gynddylan, which means "Cynddylan's hall". This would likely be the political centre of Pengwern. One stanza reads, "The Hall of Cyndylan is not pleasant/To-night, on the top of Carrec Hytwyth,/Without lord, without company, without feast!", did you catch that? The author of the poem has just told us where the location of the hall is. The University of British Columbia, unlike the website I found the full poëm on, tends to use modern rather than middle Welsh proper nouns. But according to them, Carrec Hytwyth just means "strong rock". This version also translates "loegrians" as just "English". The issue is, the normal word for English in Welsh is "sais", and the poem uses Lloegrwys, which is more literally something like "England-ese" meaning people from England rather than some sort of linguistic identity or the Anglo-Saxons. However, it's probably just for metrical reasons as we can actually date Cynddylan's rule to include at least one year from 654-655, because he killed Peada's son. This is after any sort of Celtic polity called Logres may have existed and long after the majority of the midlands were taken by the Mercians.
For the llocation of Pengwern, we also have, "Have I not gazed from Dinlle Wreconn on the patrimony of Ffreuer?". This is the connection that people have siezed on most, as Wreconn is either the Wrekin or Wroxeter. It could be either. Cambrian Chronicles thinks this is an English name the author has used but I disagree. While he is more qualified to be talking about this than I, he mentions that in Welsh Viriconium would become "Gwregon", or the like. Except, middle welsh likes spelling voiced plosives using their voiceless equivalents in postvocalic position. Anyway, this name alone could be Wrexham, The Wrekin, or Wroxeter. This may also be what pseudo-Heled refers to as "The White town", this is "between Tren and Trodwyd", and "between Tren and Traval",
I do not know any of these rivers, except the idea that tren = tern. But Wrexham isn't near any such named rivers. For the Wrekin, it's near the Tern, and could be a place she looked out from, but if it is that, then it cannot be the white town, as it is said by Pseudo-Heledd to be in a valley, and the Wrekin isn't.
Allow me to quote a stanza of Pseudo-Heledd's on the fate of the town from an alternate translation: "The fair town on the slope of the woods,/this was always its fate:/on the surface of its grass, its blood." This fair town is what is beïng destroyed, this is likely the same event as the earlier in the poem "Of Cyndylan; Llys Pengwern, is it not in flames?/Woe to the youth that longs for good fellowship."
The last option—Wroxeter could be it, but apparently it was abandoned soon after Roman Rule ended. Judging by the fact it was burned, this should leave archaeological remnants, a burn layer in the late 7th century.
However, if we look at another text, we can find a list of brythonic cities--Historia brittonum, we do see Cair Guricon, which could be the Urecon of Pseudo-Heledd. As Cambrian Chronicles says, this would be from the English name, of Wreocon Ceaster, but wouldn't this be borrowed as a diphthong? Anyway, it's a loan back from originally brythonic, and it could be that Pseudo-Heledd spoke some weird diälect. Regardless, Viriconium was abandoned in the 6th century, so it's not that. Whitechurch is also in Shropshire, but nowhere near the Tern. Maybe it was like Uxacona?
The main argument for Wroxeter is that it was the capital of the Cornovii, and there's not really a better candidate in the area anyway, except the dates ddon't line up. However, the fact borders after the roman period generally followed iron age lines, suggests continuïty between pre- and post-roman polities, so the people who ruled Viriconium were pobably in charge of Pengwern. Thus, it could be some undiscovered place the people who abandoned it went to. At the very least, you would expect burn layers, which could be in some undiscovered site.
