De Excidio et Conquestu Britanniae

De Excidio et Conquestu Britanniae (Latin: On the Ruin and Conquest of Britain) is a work written in Latin in the late fifth or sixth century by the British religious polemicist Gildas. It is one of the most important sources for the history of Britain in the fifth and sixth centuries, as it is the only significant historical source for the period written by a near contemporary of the people and events described. The usual date that has been given for the composition of the work is some time in the 540s, but it is now regarded as quite possibly earlier, in the first quarter of the sixth century, or even before that. Most scholars continue to favor a date c. 530-545, as supported by reports of his death in the various Welsh and Irish annals. The oldest manuscript is Cottonitellius A of the tenth century, damaged by fire in 1731, but used by Theodor Mommsen in his edition of his edition. Other manuscripts include the Cambridge University Library MS Ff. I of the twelfth century and the Ddd I of c. 1400.