The discovery was made by amateur archaeologist Jonathan Clemes while searching for a secret tunnel in the grounds of Prideaux Place, an Elizabethan manor house at Padstow.
Mr Clemes regularly works with TV’s Time Team and carries out a lot of excavations on the Prideaux estate.
He said: “I knew I was on to something when I found a papal bulla in the field close by. It’s a type of lead seal which was always a good indicator of a holy well being in the area. So we started excavating and found this ancient well and we feel there is a good chance that this could be St Petroc’s well.”
St Petroc arrived in Padstow in the 6th Century, having travelled by coracle from Wales. According to legend, he found reapers at work on a chapel for St Samson. The reapers answered St Petroc’s greeting rudely, saying he could best serve their needs by providing water, whereupon he struck a rock and “so gushed forth a fountain”.
Padstow vicar Chris Malkinson said: “It’s very exciting if it does turn out to be a holy well and I’ll be thrilled to bits if they call it St Petroc’s well. The name has a strong association with both the Anglican and the Catholic communities here.”
Local historian Barry Kinsmen said: “Holy wells are not that unusual here – the difficulty will be proving that this is indeed St Petroc’s well.”