Llywelyn ap Seisyll

Llywelyn ap Seisyll, who died in 1023, was a ruler of the 11th-century Welsh kingdoms of Gwynedd, Powys, and Deheubarth. He was the son of Seisyll, a figure about whom little information is available. Llywelyn emerged in historical records in 1018 when he gained control over Gwynedd and Powys after defeating and killing Aeddan ap Blegywryd along with his four sons.

In 1022, Llywelyn contested Rhain the Irishman’s claim to Deheubarth, leading to a battle at Abergwili where Rhain was killed, and Llywelyn subsequently took over Deheubarth. His reign is noted in the Brut y Tywysogion as a prosperous one, earning him the title ‘King of the Britons’ by the Annals of Ulster. Llywelyn passed away in 1023, and his son Gruffydd did not immediately succeed him, possibly due to his youth at the time.