Different sources show different years for the death of Lywarch Hen, including 620 and 634.
The son of Elidyr Llydanwyn, Llywarch the Old was the last King of South Rheged. Driven out by invading Saxons, he and his large family fled to Penllyn in Powys where he became a renowned poet in early 7th century Britain. The best known poems attributed to him are those lamenting the deaths of his cousin, Urien Rheged, Cynddylan of Pengwern and Llywarch's own sons. He was apparently present at the former's assassination, and it was left to Llywarch to recover the unfortunate Urien's head! Traditionally Llywarch had a huge family, though the numbers vary according to the source.... 2
Llywarch Hen is believed to have been an historical sixth century prince in the Old Northern Celtic kingdom of Rheged (an area of south-western Scotland today). He was the cousin of King Urien of Rheged, to whom Taliesin is thought to have been a court poet.
The core of the poetry is judged to have been written in the ninth or 10th century. It was previously believed that the poetry was written by Llywarch, but it is more likely that he is just the protagonist in the poems written about him by an unknown poet or poets of the Cynfeirdd.
Canu Llywarch Hen takes the form of a cycle of englynion, the oldest recorded Welsh metrical form that dates from as early as the ninth century. Most of the Llywarch Hen poetry exists in the Red Book of Hergest.
In the poem Dym kywardyat unhwch, The Death of Urien, Llywarch is noted as having been present at Urien of Rheged's death, and was responsible for reclaiming the head from his body after his assassination.
Another part of the poetry presents Llywarch as a petulant old man, whose demands on his 24 warrior sons subsequently lead to their deaths on the battlefield. It is only after the death of his last remaining son, Gwên, that he realises how selfishly he has treated his offspring and how his pride, arrogance and pursuit for renown were wrong. In this instance, the poetry of Llywarch Hen is almost anti-heroic when compared to the heroic nature of Aneirin's Y Gododdin. 3