In the Book of Taliesin we have the poem entitled Trawsganu Kynan Garwyn mab Brochvael. which has the following line:
kat yg cruc dymet. aercol ar gerdet.
A battle in Crug Dyfed, Aergol flying.
This poses a problem of chronology as Aergol Lawhir was of gen. -2, see Why Bartrum’s dating of the Demetian Arthur is wrong, whereas Cynan Garwyn was of gen. 1, see HG 22 below.
The chronology indicated by the above table looks sound for the following reasons. The Annales Cambriae tells us that Selyf died at the battle of Chester in the year 613:
Gueith Cairlegion, et ibi cecidit Selim filii Cinan.
The Annals of Tigernach, refers to the same incident under the 611:
Cath Caire Legion ubí sancti occissi sunt, et cecidit Solon mac Conaín rex Bretanorum et Cetula rex cecidit. Etalfraidh uictor erat, qui post statim obít.
This statement provides the added information that another death at Chester was that of Cadwal Crysban, the king of Rhos, who would have been younger than Selyf. The victor was Aethelfrith. Triad 25 describes Selyf as one of the Three Battle-Rulers of the Island of Britain.
Cynan’s daughter, Tandreg Ddu, was the wife of Cadfan and the mother of Cadwallon. Brochwel was married to Arddun ferch Pabo Post Prydyn and was the son of Cyngen by Tudglid ferch Brychan.
However, if we now look at HG 27 we can see that Cynan and Cyngen have been interchanged, see The Powysian lineage. This is likely to be a corruption. Is it possible that a similar thing happened with the poem and a battle fought by Cyngen, who was of the same generation as Aergol, was wrongly attributed to Cynan?