Dictionary of Welsh Biography

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LLYWELYN ap SEISYLL (d. 1023 ), king of Deheubarth and Gwynedd .

Nothing is known of his father, but his mother, Prawst , was, according to late pedigrees, the daughter of Elisedd , a younger son of Anarawd ap Rhodri Mawr . Since he himself m. Angharad , daughter of Maredudd ab Owain ap Hywel Dda , he had distant claims to succession in both Deheubarth and Gwynedd , which in the circumstances of the time could be translated into reality by a leader of force and ambition. Such a man was Llywelyn , and by his defeat of the usurper, Aeddan ap Blegywryd , in 1018 , and of Rhain , an Irish pretender, in 1022 , he became master of the south. He also extended his rule for a few years over a large part of Wales , a memorable period in Welsh annals judging from entries in the chronicle. His chief claim to fame, however, is the fact that he was the father of Gruffudd ap Llywelyn , whose notable career was made possible by the example of the father, and whose claim to power was largely based on the short ‘de facto’ overlordship of Llywelyn .


  • A History of Wales: from the Earliest Times to the Edwardian Conquest ;
  • The Transactions of the Honourable Society of Cymmrodorion , 1899-1900.


Professor Thomas Jones Pierce, M.A., F.S.A., (1905-1964), Aberystwyth

Published date: 1959