St. Aaron

The first of many, many saints in an A-Z of all saints happens to be quite appropriate for what I was thinking of. A native of Britain who moved to Brittany.

(Or, just got confused between Britain and Brittany, and though it was more or less the same thing.)

And he becomes a hermit, which must be the Route 1 of sainthood. You don't need to do anything in particular other than go a bit mad and live in a cave.