Historians have known the ‘Gododdin’ ever since Skene's edition and translation in the Four Ancient Books of Wales (1868)' and have realized the possibility that its claim to be the work of a sixth-century British poet may be in some form true. The text however was so obscure and in parts corrupt, and hence Skene's and other translations so plainly unreliable, that few have cared to deal boldly with it. Now comes Professor Williams' life-work, his edition of and introduction to the Book of Aneirin, in which he establishes as satisfactory a text as is ever likely to be made, and solves the great majority of the difficulties of interpretation. The importance of this book cannot be overestimated, and since the whole is written in Welsh a full description is necessary.