The Annales Cambriæ record that "Maredut filius Owein" laid waste to "Hewed", undated but apparently in 991 from the context.
He succeeded in 986 as MAREDUDD King of Gwynedd. The Gwentian Chronicle records that "the government devolved on "Meredydd son of Owain son of Hywel the Good" after "Einion son of Owain" was killed in 982. He succeeded in 988 as King of Deheubarth.
The Chronicle of the Princes of Wales records that "Maredudd son of Owain killed Cadwallon son of Ieuav victoriously and subjugated his territory, to wit the Isle of Mona and Meirionydd, and all the districts of Gwynedd he subdued by extreme craft and cunning" in 985. The Chronicle of the Princes of Wales records that "Maredudd son of Owain paid to the black Pagans a tribute of one penny for each person" in 988. The Chronicle of the Princes of Wales records that "Edwin son of Einon with Eclis the Great a Saxon prince from the seas of the south devastated all the kingdom of Maredudd, to wit Dyved and Ceredigion and Gower and Cydweli…and Maredudd hired the Paganswilling to join him and devastated Glamorgan" in 991.
The Chronicle of the Princes of Wales records that "Maredudd son of Owain the most celebrated king of the Britons died in 998. The Gwentian Chronicle records that "Meredydd son of Owain died, which was the occasion of better times for peace and government in Wales" in 994. The Annales Menevensis record that "Mareduc filius Owein" died in 1000. The Annales Cambriæ record that "Maredut filius Owini" died, undated but apparently in 999 from the context. 1
He succeeded his aged father as sole ruler of Deheubarth in 986, and in the same year repeated the achievement of his grandfather by reuniting Gwynedd and Deheubarth for the period of his reign. In spite of domestic disharmony, he impressed contemporaries by his bold and aggressive leadership against Saxon and Dane. His greatest claim to fame rests, perhaps, on his relationship to Gruffudd ap Llywelyn, whose mother, Angharad, was Maredudd 's daughter. 2