Tree ring dating and archaeology
Research Notes: King of Gwynedd and Powys and Seisyllwg From A History of Wales, pp.
78-79:"A chain of marriages begins around 800 when Gwriad, a native of the Isle of Man, who perhaps had links with the Men of the North, married Esyllt of the line of Maelgwn Fawr; their son, Merfyn, became kind of Gwynedd in 825 on the death of Esyllt's uncle, Hywel ap Rhodri, the last of the male descendants of Maelgwn Gwynedd.
Rhodri became ruler of Gwynedd in 844 on the death of his father, of Powys in 855 on the death of his uncle, Cyngen, and of Seisyllwg in 871 on the death of his brother-in-law, Gwgon; he died in 878, king of a realm extending from Anglesey to Gower."A later generation of chroniclers hailed Rhodri ap Merfyn as Rhodri Mawr (Rhodri the Great), a distinction bestowed upon two other rulers in the same century--Charles the Great (Charlemagne, died 814) and Alfred the Great (died 899).
This was the first time a ruler of Gwynedd had accepted the supremacy of an English king, and formed the basis for the homage which was demanded by the English crown from then on. By becoming the ruler of Powys, his mother's land, he inherited the old struggle between that kingdom and Mercia.In 894 Anarawd was able to repel a raid by a Danish host on North Wales, and the following year raided Death Notes: Killed by the Saxons. Although Offa's Dyke had been constructed in order to define the territories of the Welsh and the English, this did not prevent the successors of Offa from attacking Wales...The pressure upon Powys continued; after 855, Rhodri was its defender, and he and his son, Gwriad, were killed in a battle against the English in 878." ) was born circa 880 in Dinefwr Castle, Llandeilo, Carmarthenshire, Wales and died about 950 about age 70.83: "If the intention of the rulers of Dyfed and Brycheiniog in seeking the patronage of Alfred was to remain free from the clutches of the house of Rhodri, they failed.About 904, Llywarch ap Hyfaidd, king of Dyfed, died; his kingdom came into the possession of Hywel ap Cadell ap Rhodri, the ruler of Seisyllwg and the husband of Elen, Llywarch's daughter.