St. Similien, lived in the early fourth century and was the third bishop of Nantes, who, according to St. Gregory of Tours, was given the title of grand confessor.
In an old book on Breton saints, he is summarized as follows: "This worthy prelate remained unyielding and steadfast during the cruel persecutions of Diocletian and Maximian, and wisely led the ship that was entrusted to him.
As the winner of the protracted storm, he was the first bishop in Nantes, so drenched in the blood of Christian martyrs, the light did break through better times.
The siege lasted sixty days until one night, the besiegers saw a procession of white-clad figures from the church, each carrying a candle.
They then saw a similar procession from the Church of Saint Donatian, and the Saxons were thrown into such panic that they abandoned their positions and fled.