The big conversion happened during a drought. The Cenomani were desperate for water, so Julian took his staff, hit a rock, and a spring gushed forth. In gratitude, King Defensor (not very Gallic, I know) of the Cenomani accepted baptism and offered part of his palace (a relative term) as a cathedral (another relative term).
Instant Christians. Just add water.
Not everyone was sold on the new faith, though. Julian had to keep the miracles coming to win over the whole group. Hey bishop, raise Ortecorix from the dead, would you? Oh, Julian, I think my daughter has demons again. Would you drive them out for her?
|Nice cathedral you've got there, Julian.|
He retired to a hermitage when he felt he wasn't up to bishoping anymore. Upon his death, a massive funeral was held and a church was built over his burial site within the century, suggesting local veneration as a saint.
King Henry II was born in LeMans and baptized at the Cathedral of Saint Julian, which accounts for the English churches that bear his name.