He was the first Archdeacon of Anglesey before having been elected bishop before 12 December 1267, consecrated at Canterbury, and received possession of the temporalities 5 January 1268.
[1] By the time that Anian was elected bishop, Llywelyn ap Gruffudd, the Prince of Wales, entered into agreements regarding territorial disputes over the rights of the sees of St Asaph and Bangor and relied on the bishops as peacekeeping intermediaries with King Edward I of England,[2] but soon asserted control over the church's property and land.
[5] Anian and the Bishop of St Asaph notified Llywelyn that they disagreed with his treatment of his brother, David, in 1274.
[6][better source needed] Having sided with the king, he lived at the St. Albans Abbey in England for ten years beginning in 1277, during a period of unrest in Wales.
He received a share of the tithes of royal dues in Englefield and legal rights in the lands of the bishopric for having helped with the settlement of North Wales.