Do de Carduel
Deon, Deu, Dieu, Does, Doon, Dos, Due, Landinas?
He served as Arthur’s castellan of Cardueil and, later, London. He fought against the Saxon invasion at the beginning of Arthur’s reign. Malory calls him 'Cardol' (Cardueil), confusing his home with his name.
This is according to D.D.R. Owen's translation, but I suspect that "Do" was either a variant of or a scribe's error for "Dieu". Else the post-Chrétien writers confused a human character's name with that of the Deity.