Years ago now - in fact, as long ago as 2021 - I had made what I thought to be an important discovery regarding the location of Caer Dathal:
Unfortunately, I was told that this could not be right by an expert at the Historic Place-Names of Wales project with the RCAHMW. According to this person, Dinas Emrys was never in Arfon, but had been in Dunoding or, more precisely, the Eifionydd portion of Dunoding.
As a result of this information, I abandoned the idea and instead pursued a somewhat satisfactory argument to prove Caer Engan in Nantlle was Caer Dathal. I was particularly happy with the idea, as it Dathal be from Irish Tuathal, who had somehow been corrupted, despite the Welsh cognate Tudwal being present in the St. Engan context. Still, it was better than nothing, and made some sense of the movements of the primary characters of MATH SON OF MATHONWY to and from Caer Dathal.
Well, I never completely let go of my Caer Dathal = Dinas Emrys theory. And only recently I had another go at making sure the latter fort was never in Arfon.
As it turns out, it was. While it is true Beddgelert parish spread through several cantrefs and commotes, the fort itself was definitely within the cantref of Arfon.
"The main military center of the comwd was Dolbadarn Castle , which defended Nant Peris at the foot of Yr Wyddfa . In Nant Gwynant in the south-east stood the old defense of Dinas Emrys which is associated with Myrddin , king Gwrtheyrn and the history of the Red Dragon and the White Dragon."
I have had this confirmed by several good sources, maps and personal correspondence from Welsh experts in historical and political geography.
What does this mean for my Arthurian research? Well, pretty much EVERYTHING.
Firstly, it helps us relate the two apparent pre-Galfridian references to Uther's locations found in the PA GUR, CULHWCH AND OLWEN and the HANESYN HEN.
The PA GUR seems to relate Uther, via Mabon son of Modron, his servant, to the Ely River in Glamorgan. I have shown that Gileston just the other side of the River Thaw from the old kingdom of Penychen, which included the Dinas Powys and Caerau forts, had been called the Church of Mabon of the Vale. And that between that church and the Penychen forts was to be found Elleti, the place of Ambrosius/Emrys.
CULHWCH AND OLWEN tells is that Uther had relatives at Caer Dathal.
The HANESYN HEN tract adds that Gwyn Godybrion of the Ely was a son of Iaen from Caer Dathal.
It also tells us Arthur took a wife from Caer Dathal.
A couple of other sources may also be important in localizing Uther and Arthur in NW Wales.
A Stanza of the Grave puts the tomb of Mabon in Nantlle, not far from Dinas Emrys.
Finally, the "Dialogue of Arthur of the Eagle"'s Eliwlad son of Madog son of Uther is patterned after Lleu of Nantlle, and there is even an identical placename involved (Cutmadoc in Cornwall, Coed Madoc in Nantlle) which would appear to suggest that the character has been relocated from the north to the south.
As we know, Ambrosius and Uther were closely associated in the Galfridian tradition. So much so that both kings are buried at Stonehenge hard by Amesbury, a place-name linked to the personal name Ambrosius. The two urns at Dinas Emrys contained 'dragons' originally in the sense of the cremated remains of two great warrior chieftains. We thus have a linking in story of Dinas Emrys with the Burg of Ambrius.
Now, it is not my purpose in this short blog piece to delve once again into the identities of Ambrosius and Uther (who might even be the same mythological person - although there are other possibilities). But what I can say is that it makes a great deal of sense to identify the Caer Dathal of Uther with the Dinas Emrys of Ambrosius. And, in fact, knowing as I do now that Dinas Emrys was in Arfon, I consider the mystery of the whereabouts of the lost fort of Dathal solved.