In 1846, together with
Harry Longueville Jones (1806–1870), another cleric and antiquary, Williams founded the
Cambrian Archaeological Association, whose journal,
Archaeologia Cambrensis, he edited until 1853, when he and Jones quarrelled over editorial policy. He also published an edition and translation of the
Gododdin in 1852, established the
Cambrian Journal, which he edited from 1854 until his death, and was prominent in the
Welsh Manuscripts Society, editing four of its publications. The
Llangollen Eisteddfod of 1858, which he organized together with
Richard Williams Morgan ('Mor Meirion', c. 1815 – c. 1889) and
Joseph Hughes ('Carn Ingli', 1803–1863), caused much derision and embarrassment; Williams' own family won several prizes, and
Thomas Stephens (1821–1875) was adjudicated against because he suggested that the story of Madog ab Owain Gwynedd's American expeditions was not true. Williams was nevertheless considered for the chair of Celtic at
Oxford University, and he was appointed by the government in 1858 to complete the editions of the medieval Welsh chronicles
Annales Cambriae and
Brut y Tywysogion, which had been left incomplete by
Aneurin Owen (1792–1851), and which were published in 1860. His editorial work was later criticised by academics due to his lack of the diplomatic skills for interpreting medieval manuscripts. ==Religious appointments==