The controversial Iolo Manuscripts claim an older foundation dating to Saints Dyfan and Fagan, said elsewhere to have missionized the court of King Lucius of Britain on behalf of Pope Eleutherius around AD 166.

[2] The present-day St Fagans (referenced in the manuscripts as "Llanffagan Fawr") is now a village near Cardiff.

[2] Originally Celtic Christians, the bishops were in full communion with the Roman Catholic Church from 777 until the Reformation.

[citation needed] This appears to have been a simple reaction to the claim of St David's to the archiepiscopal title.

The bishopric and diocese of Llandaff now constitute part of the Church in Wales within the wider Anglican Communion.

She legally took up her See as of the Sacred Synod to confirm her election;[5] which occurred on 19 April 2023 at Holy Trinity, Llandudno.