The records of the British past were handed down
through oral tradition (in the form of trained bards who specialised
in memorising such material). Only a small part of this oral tradition
was ever committed to writing.
Furthermore, the distinction that modern readers
automatically make between history and literature was by no means
Add to this all the misty problems of sources and
dating, or of authors' intentions in writing their works, and the
interpretation of those relatively few texts that have survived to
the present day have become a formidable exercise.
This is immediately apparent when studying the first
and most substantial account of Arthur's deeds in the Welsh records.
This account took the form of an book which was written or compiled
around the year 829, entitled Historia Brittonum (The History
of the Britons). It is often ascribed to a certain Nennius, although
some scholars would argue that he (if he existed) had no part in it. 
This work is far from being a history; a later editor
thought that the author had 'piled together everything [he] could find',
and what can really be discovered from it concerns the culture and
traditions of the Welsh people in the late eighth and early ninth
century, which is the period in which it was put together.
It is an attempt to explore the Welsh past, but its
author is not writing in what would now be considered an historical
manner; there is no real chronology, and little attempt is made to
examine the sources critically such as can be detected in the work
of his Anglo-Saxon predecessor, Bede.
The writer is more concerned with the ideology of
the present: he portrays the Welsh as a race of noble descent, capable
of heroic deeds, treacherously driven out of their rightful lands by
All of this had considerable relevance to the political
ambitions of the Welsh at the end of the eighth century, when there was
the hope of a revival of their fortunes under Rhodri Mawr, king of
Gwynedd, who was uniting the country peacefully.
So the Historia Brittonum is more a record of
developing tradition, drawing on heroic poetry, on legends about places
and names, and on oral tales, a tradition which is by no means static
but which is being elaborated all the time.
But, underneath the synthesis of available material
made by the author of The History of the Britons, there does
appear a dimly discernible historic record which has been confirmed by
at least two brief entries in a set of year-by-year entries in the
Annales Cambriae (the Annales of Wales), for 516 and 537.
Nennius' material needs to be read with care because
he cannot be entirely trusted, but there is a basis of truth within his
text that can be extracted with extreme care.