Unfortunately we cannot trust the traditional English chronology of the period.

As to the date of Gildas, cf.

W.H.

Stevenson, _Academy_, October 26, 1895, &c.; I see no reason to put either Gildas or any part of the _Epistula_ later than about 540.] It is this Celtic revival which can best explain the history of Britannia minor, Brittany across the seas in the western extremity of Gaul.

How far this region had been Romanized during the first four centuries seems uncertain.