 He became infamous for his hostile reaction to Irish missionaries.He opposed Breage's mission (although Sabine Baring-Gould placed its arrival around 500), first compelling them to land at Reyvier instead of Carnsew and then later martyring several of its members, including Ia of Cornwall; Saint Gwinear met with a similar fate, being thrown with his followers into a pit of reptiles.After decades of exile, Tewdwr returned to Brittany and defeated Macliau and his oldest son Jacob in 577.