Cyndrwyn died before 642 when his sons, chief of whom was Cynddylan, joined Penda of Mercia in the defeat of King Oswald of Northumbria at the Battle of Maserfield (Welsh: Maes Cogwy), which may have taken place just outside Oswestry.
[6] The later and less reliable Canu Heledd suggest that Cynddylan died defending Powys from English invaders at a place called Tren,[7] generally understood as the River Tern in Shropshire.
[9] Strikingly, it is actually addressed not to a king of Powys, Cynddylan's home, but of Dogfeiling, a sub-kingdom of Gwynedd near to Rhuthun in the middle of Denbighshire, based in Aberffraw, which suggests a rather complex political context for its composition.
Davies's copy includes a variety of old spellings consistent with the thirteenth-century conventions attested in the Black Book of Carmarthen, but the orthography is mostly modernised, not always accurately, making the poem particularly tricky to interpret.
This cycle of englynion takes the form of Princess Heledd lamenting the destruction of her home and the death of her family (including her brothers, one of whom was Cynddylan, her sister Ffreuer and the royal court), at the hands of the English.
While some historians have taken the cycle as reliable evidence for events in the sixth century, it is now thought to be a reimagining of historical people and places which owes much more to the political situation of its time of composition.