He was instructed in the art of poetry by, among others, the bard Gruffudd Hiraethog, who was later recorded as believing that "There is nothing that Wiliam Llŷn does not know",[3] and he was awarded the miniature silver chair at the 1567 eisteddfod as the best poet.
[3][5] He belonged to the last generation of poets who wrote for members of the native aristocracy,[6] finding patrons as far away as Brecknockshire and Anglesey, though most lived in the neighbouring counties of Merionethshire, Montgomeryshire, Denbighshire, and Caernarfonshire.
[10] Especially notable are his elegies on his master, Gruffudd Hiraethog, and his fellow-bards Owain ap Gwilym and Siôn Brwynog [cy], which are considered to be among the best poems of their kind in the Welsh language.
[7] Though his work is decidedly conservative, deeply indebted to the bards of the past, he nevertheless does show signs of the changing times, as in his familiarity with Greek poetry and possible espousal of Stoicism – both Renaissance characteristics – and in his heavy use of English loan-words.
Robert Williams judged that he "excelled all the bards of his time in sublimity of thought, and poetic fire",[13] and Daniel Lleufer Thomas wrote that "he is generally considered the greatest Welsh poet in the period between Dafydd ab Gwilym and Goronwy Owen".