St Teilo was born at Penalun (Penally) around about AD500. He was the son of Prince Ensich ap Hydwn – grandson of King Ceredig of Ceredigion.
He studied from a young age under St Paulinus of Wales at Wincdi-Lantquendi (thought to be Whitland) where he met and became a close companion of St David.
Along with companions Aeddan and Ysfael, the four traveled to St Davids (known as Mynyw) where Dewi founded his famous Abbey.

A tale is told of how Teilo and Aeddan were called away from their books in the cloisters of St Davids to collect wood for the monastery’s fuel store. Not too pleased at being disturbed while studying they took their axes off into the woods. However they found their task much easier than they expected as two tame stags helped them by carrying the wood home for them.

Teilo succeeded St Dyfrig as Bishop of Glywysing & Gwent, and probably moved this Bishops seat to his foundation at Llandeilo Fawr.

After the yellow plague swept through Wales around AD549 Teilo took the survivors of his community to Dol in Brittany where he and St Samson planted groves of fruit trees between there and Cal. The groves are still there today and are called the groves of Teilo and Samson.
While Teilo was in Brittany it is said he was persuaded by his brother in law King Budic II to save the country from being destroyed by a winged dragon. The creature was apparently tamed by Teilo who then tied it to a rock in the sea.

After Dewi’s death Teilo became one of the most holy men in Wales. Teilo died at the abbey of Llandeilo Fawr on February 9th but the year of his death is uncertain. His tomb now lies in Llandaff Cathedral to the right of the altar while his skull is still kept in the south chapel.