St Deiniol may have come from Northern Britain and taught by St Cadoc and consecrated bishop by St David. He founded the monastery of Bangor Fawr in Gwynedd on the Menai Straits and of Bangor Iscoed on the Dee in Clwyd. He attended the Synod of Brevi in 545; he has a holy well and picturesque chapel (later made a folly?) at Penally. He was buried on Bardsey.
Troparion
You gathered many monks to Bangor on Dee
and they shone forth as a great light to North Wales
as Bishop you taught the way of salvation.
Wales still needs your prayers, holy father in Christ!