St. Gildas was a monk who chronicled the history of the British isles from the time near the end of the Roman era to the coming of the Saxons. He lived approximately from 500 – 570 AD. His most famous work is the De Excidio et Conquestu Britanniae (On the Ruin of Britain). It is an important piece of writing as it is one of few contemporary writings of the period surrounding sub-Roman Britain. I have linked to the translation of the document below:
