Gildas's 'De Excidio Britanniae' is the prime source of our knowledge of post-Roman Britain, but because it is such an isolated text, for which we have no obvious historical, geographical or cultural background, it is a work whichraises more questions than answers. Much effort has been expended on extracting historical facts from 'De excidio', but Gildas did not set out to write history as we understand it. The common approach of the contributors to thisvolume is to look at tha author and his text on their own terms, for themselves rather than for the items of evidence which we can get out of them. Who was Gildas, and what was his position in society? What was his intellectual background - what he had learnt of Latin and Christian culture through his education, and what did he know of British language and literary traditions? What audience was he adressing? All these questions can be given some kind of answer by a close study of the text of the 'De excidio'. But there is also important evidence from Continental sources on early fifth-centyry Britain, and from Irish sources on Gildas's own repuation and career. This is a volume which no student of post-Roman Britain can afford to ignore, it does not attempt to present clear-cut conclusions or optimistic certainties, but establishes a basis on which further research can be carried out.