Ambrosius Aurelianus
Fleuriot's book "Les origines de la Bretagne" defended a "two wave" model of British immigration into Brittany and argued that the legend of King Arthur arose from the life of Romano-British leader Ambrosius Aurelianus, who was known in Gaul as Riothamus. Fleuriot came into conflict with François Falc'hun's claim that Breton was essentially native Gaulish, only influenced by the incoming British language. However, he accepted that Breton had been influenced by surviving local forms of Celtic.