The Historia Brittonum (History of the Britons) appears to have originally been compiled c.829. None of the surviving manuscripts, of which there are about 40, is earlier than the 11th century. In some manuscripts, the author, in a preface, introduces himself as Nennius, "disciple of Elvodugus". Elvodugus being Elfoddw, who, in his 'Annales Cambriae' obituary (the year 809), is described as "archbishop in the Gwynedd region". It seems likely, however, that the attribution to Nennius is a later (mid 11th century) accretion. Regardless of its provenance, the preface does accurately sum up the haphazard nature of the work:
"I, Nennius, disciple of Elvodugus, have endeavoured to write some extracts which the stupidity of the British nation had cast away, because teachers had no knowledge, nor gave any information in their books about this island of Britain. But I have made a heap of all that I could find, as well from the annals of the Romans as from the chronicles of the sacred fathers, Hieronymus, Eusebius, Isidorus, Prosper, and from the annals of the Scots [i.e. Irish] and Saxons, and from our ancient traditions."
In 'Wales in the Early Middle Ages', Wendy Davies writes:
"It is impossible, therefore, to generalize about the value of the Historia Brittonum. On the one hand it provides first-hand evidence of the attitude to history writing of a Welshman of the early ninth century. On the other it presents us with edited documents of varying dates and provenances whose origins are not yet sufficiently understood ..."