The earliest Life of Petroc states that he was the son of an unnamed Welsh king. This was rewritten at Bodmin in the twelfth century in a version known as the ‘Gotha Life’ which states that he was a son of King Glywys of Glywysing (Orme 2000, p. 215) and a brother of Gwynllyw, and there are local dedications to him at St Petroc near Pembroke and Ferwig near Cardigan. He has also given his name to Llanbedrog, a village on the Lleyn peninsula. He studied in Ireland where he is said to have been the teacher of Saint Kevin.
After studying, he began his mission to Cornwall, where he is associated with monasteries at Padstow and Bodmin. The name of the earlier monastery was Lanwethinoc (the church of Wethinoc an earlier holy man). Padstow, which is named after him (Pedroc-stowe, or ‘Petrock’s Place’), appears to have been his major cult centre for some time. Some time after the middle of the ninth century Bodmin became the major centre for his veneration and his relics were moved there,[1] with the Bodmin monastery becoming one of the wealthiest Cornish churches by the eleventh century.[2] There are other dedications to him in Cornwall, including Little Petherick, and he is even said to have converted its king, Constantine of Dumnonia, to Christianity. After thirty years, legend says that he went on the pilgrimage to Rome by way of Brittany.
Upon his return Petroc is said to have passed through Devon, where ancient dedications to him are even more numerous: a probable seventeen (plus Timberscombe just over the border in Somerset), compared to Cornwall’s five. The position of churches bearing his name, including one within the old Roman walls of Exeter (Karesk), are nearly always near the coast reminding us that in those days travelling was done mainly by sea. The Devonian villages of Petrockstowe and Newton St Petroc are also named after Saint Petroc.
The legendary tales surrounding Petroc are exceptionally vivid and imaginative (giving him a second pilgrimage, travels to India, taming wolves) and may represent interpolation from pagan tales.
In iconography, Petroc is usually shown with a stag. His feast day is June 4. His major shrine was always at St Petroc’s Church, Bodmin. In 1177, a Breton stole his relics from Bodmin and gave them to the Abbey of St Meen. However, Henry II restored them and, though the relics were thrown out during the English Reformation, their beautiful ivory casket is still on public display in the church. With Saint Piran and Saint Michael, he is one of the patron saints of Cornwall.
From Wikipedia