Bartrum's "Welsh Genealogies". Bartrum's "Pedigrees of the Welsh Tribal Patriarchs" 11 note: "Llywarch Howlbwrch, born c. 1020?, was ancestor of a tribe in Denbighshire. He is presumably the Llywarch Olbwch mentioned in Hanes Gruffudd ap Cynan as chief chamberlain and treasurer to GRUFFUDD AP LLYWELYN. His wife, Tangwystl, described as a prophetess, greeted GRUFFUDD AP CYNAN, her relation, on his arrival in Wales from Ireland in 1075."