The Kings of Gwynedd were the dominant force in Wales from the 9th century, but their own laws of succession, with their realms being divided between their male heirs, repeatedly confounded their ambitions to rule all of Wales. In addition, they had to fend off repeated Saxon invasions, usually from Mercia, and Viking incursions, usually via Anglesey. Rhodri Mawr (‘the Great’) managed to annex both Powys and Seisyllwg, before being killed by the Mercians in c. 878, whereupon the kingdom was parcelled out between three of his sons. Hywel Dda (‘the Good’) and Maredudd ap Owain both united Wales, excepting the southeast. It was Grufydd ap Llywelyn who finally, albeit briefly, succeeded in becoming ‘King of all Wales’, from 1057–63. His reward was a joint amphibious invasion by the Anglo-Saxon Godwinson brothers, Harold (the future King Harold II of England) and Tostig. Grufydd was deposed, and killed in his Snowdonian hideout.
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