The Welsh Christian monk Nennius wrote around 800 A.D. the "Historia Brittanum" which is the first publication to contain a mention " Arthur" by name as a hero. Well, Nennius was probably an early ninth century Welsh monk, and probably wrote it. Historia Brittonum (History of the Britons) is a strange assortment of texts covering the ancestries of kings, geography, the lives of saints. It mentions Julius Cæsar, Ambrosius Aurelianus, Arthur, Patrick, and other figures. Nennius says he was a pupil of Elbodugus ( bishop of Bangor and known to have have died in 809)
The Historia Brittonum has been controversial as to its date and origin. Nennius has been described as "unrestrainedly inventive" with this work. On the one hand Nennius apparently had access to no-longer available 5th century sources, but on the other hand can Nennius be entirely trusted as a thoughtful compiler of history. Apart from his native Welsh and his clerical knowledge of Latin, ‘Nennius’ seems to have understood both Old English, and Old Irish.
Nennius made mistakes with dating schemes, people's names and genealogical facts. However ‘Nennius’ is nevertheless one of the earliest records of Welsh literature and history and his work is therefore very useful to researchers. The work may have in fact been compiled earlier by someone else, around the year 679. Then additions were made in following years, and Nennius may have then re-compiled the whole work around 800.
To complicate matters even further, the revision of Nennius does not exist in a complete form. The earliest existing copy is an Irish version made in the eleventh century by Gilla Coemgin. Some of the Latin copies have extracts from the original, including the preface of Nennius and some verses by him.
"Historia Brittanum" is drawn largely upon Celtic legend, written or oral. Other writings which have been used include Gildas, Jerome’s Chronicle and a lost life of St. Germanus of Auxerre. Geoffrey of Monmouth was later to extensive use of it.
The brief mention of Arthur by Nennius occurs when he describes him as being the British leader who fought against the Anglo-Saxons. The battle culminated in a victory for the Britons at the Battle of Mount Badon (Mons Badonicus). Nennius lists twelve battles with which Arthur was involved.
Nennius also mentions Arthur had a dog called Cabal, which had used to hunt boar. Nennius also mentions the burial site of Anir, the son of Arthur, killed by his own father.
Nennius also mentions Ambrosius, but not the same Ambrosius Aurelianus mentioned in the works by Gildas and Bede. This Ambrosius was another name for the boy that Geoffrey called Merlin. The story of Vortigern and Ambrosius (Merlin), the falling wall and the two fighting dragons are used in Geoffrey's works.
It has proved virtually impossible for modern researches to compile the life of Nennius
King Arthur in Literature