There have been long and sharp discussions as to the age, the country, and even the personality of the author who is generally known as Nennius. The following pages represent the chief conclusions arrived at by a German student of Celtic literature, Professor Zimmer, who in his book, _Nennius Vindicatus_, has surely vindicated his client’s right to exist, though he admits as fully as any one that client’s terrible deficiencies as a historian. We may now, then, venture to assert that Nennius, the author of the _Historia Brittonum_, was born about the middle of the eighth century, that he lived in South-East Wales, probably near the borders of Brecon and Radnor, that he wrote his book in or about the year 796, and that it was subjected, about 810, to a very early revision by a scribe who calls himself Samuel, and who lived in North Wales. For some reason or other the book had considerable popularity both in England and on the continent, especially in Brittany, but it suffered much at the hands of ignorant transcribers, and a narrative, not originally very lucid, has in some places been made almost unintelligible, owing to the transposition of some of the leaves of manuscript which have fallen out and been replaced in a wrong order. The restoration of these wrongly sorted chapters to their proper place in the book is one of Professor Zimmer’s greatest achievements. The work of an ill-informed and uncritical scribe such as Nennius evidently was,[35] subject also to all these adversities in the course of its transmission to us, and originally written three centuries and a half after the events recorded, might be considered so poor an authority as to be unworthy of our further notice. But, in the first place, we have practically no other British authority save Gildas for the events which interest us so deeply; and, secondly, the author has at one point incorporated in his work a document much earlier and much more valuable than his own. This is the so-called “Genealogies of the Kings,” which occupy sections 57 to 65 of the _Historia Brittonum_, and which, though they consist chiefly of strings of names, the ancestors of Anglian kings, are of a comparatively early date, since they bring the history down only to 679 (being thus slightly earlier even than Bede), and have this especial interest for us that we have here, imbedded in a passionately Celtic work, information otherwise lacking as to the rulers of the Anglian kingdoms of Northumbria and Mercia in the sixth century.