Welsh sources mention a disciple of the mid-8th century Bishop of Bangor, Elbodug (or Elbotus), who was the first to introduce the Roman system of reckoning the date for Easter into the Welsh church. This may be the intended Nennius.
Nennius wrote the Historia Brittonum which is the first publication to mention " Arthur" by name as a hero. 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 the burial site of Anir, the son of Arthur, killed by his own father.