The
Historia Brittonum has drawn attention because of its role in influencing the legends and myths surrounding
King Arthur. It is the earliest source that presents Arthur as a historical figure, and is the source of several stories which were repeated and amplified by later authors.
Vortigern and Ambrosius The
Historia contains a story of the king
Vortigern, who allowed the
Saxons to settle in the island of Britain in return for the hand of
Hengist's daughter. One legend about Vortigern says he tried to build a stronghold near
Snowdon called
Dinas Emrys, only to have his building materials disappear every time he tried. His advisers told him to sprinkle the blood of a fatherless boy on the site to lift the curse. Vortigern found such a youth in
Ambrosius, who rebuked the wise men and revealed that the disturbance was caused by two dragons buried underground. The tower story is repeated and embellished by
Geoffrey of Monmouth in his
Historia Regum Britanniae, though he attributes it to
Merlin, saying "Ambrosius" is the sage's alternative name. Geoffrey includes Aurelius Ambrosius, another figure mentioned in the
Historia, as a king in his own right, and also includes other characters such as
Vortimer and Bishop
Germanus of Auxerre.
Arthur's battles Chapter 56 discusses twelve battles fought and won by
Arthur, here called
dux bellorum (war leader) rather than king: Many of these battle sites are obscure and cannot be identified with any certitude. Some appear in other Welsh literature, though not necessarily explicitly connected to Arthur. Some scholars have proposed that the author incorporated the list from a now-lost Old Welsh poem, based on the fact that some of the names appear to rhyme. Others argue that the author included battles not previously associated with Arthur, and perhaps even made them up entirely. The odd description of Arthur bearing the image of the
Virgin Mary on his shoulders at Guinnion might stem from a conflation of the Welsh word (shield) with (shoulders). A similar story to that attached to Guinnion also appears in the
Annales Cambriae; here, Arthur is described as carrying "the cross of our Lord Jesus Christ on his shoulders for three days and three nights…", though here the battle is said to be Badon rather than Guinnion. T. M. Charles-Edwards argues that these accounts both refer to a single source. Other scholars, however, such as Thomas Jones and
N. J. Higham, argue that the
Annales account is based directly on the
Historia, suggesting the name of the battle was switched from the unknown Guinnion to the famous Badon, and that the icon Arthur carries was replaced with a more common one. The Battle of Mount Badon is associated with Arthur in several later texts, but not in any that predate the
Historia. It was clearly a historical battle described by
Gildas, who does not mention the name of the Britons' leader. He does however mention Aurelius Ambrosius as a great scourge of the Saxons immediately prior. Of the other battles, only the Battle of Tribruit is generally agreed to be associated with Arthur in another early Welsh source. Tribruit appears as
Tryfrwyd in the Old Welsh poem
Pa Gur?, dating to perhaps the mid-ninth century. This poem follows the story of a battle against , or
dogheads, whom Arthur's men fought in the mountains of
Eidyn (Edinburgh); in the Tryfrwyd battle they spar with a character named Garwlwyd (Rough-Gray), who is likely the
Gwrgi Garwlwyd (Man-Dog Rough-Grey) who appears in one of the
Welsh Triads. Arthur's main protagonist in the fight is
Bedwyr, later known as Sir Bedivere, and the poem also mentions the
euhemerized god
Manawydan. "The City of the Legion" may be a reference to
Caerleon, whose name translates as such, but it might also refer to
Chester, the site of a large Roman base.
Cat Coit Celidon is probably a reference to the
Caledonian Forest (
Coed Celyddon) which once covered the
Southern Uplands of Scotland. Scholar Marged Haycock has suggested that this battle can be identified with the
Cad Goddeu, the "Battle of the Trees", best known from the tenth-century poem
Cad Goddeu. Arthur is mentioned towards the end of this poem, and a fragment of a story about the battle preserved in manuscript Peniarth 98B states that the battle had an alternate name,
Cad Achren, which suggests a connection with the
Caer Ochren raided by Arthur in the earlier poem
Preiddeu Annwfn. Various writers have asserted that this chapter supports a
historical basis for King Arthur and have tried to identify the twelve battles with historical feuds or locales (see
Sites and places associated with Arthurian legend). On the other hand, Caitlin Green argues that the only identifiable battles linked explicitly with Arthur in Old Welsh sources are mythological, undermining any claims that the battles had a basis in history.
Mirabilia Attached to the
Historia is a section called
De mirabilibus Britanniae (or simply
Mirabilia for short, a Latin word meaning 'marvels, miracles'). It gives a list of 13 topographical marvels, or wonders of Britain, followed by a few marvels of
Anglesey (
Menand insulae or Mona) and of Ireland. The
Mirabilia section is thought to not be part of the original work, but to have been composed shortly after (early 9th cent.). Two of the marvels are Arthurian lore (Chapter 73 of the
Historia). since they are closer to the Welsh forms of those names. The first concerns Arthur's dog, Cabal (
Cavall in Welsh), and the footprint it left while chasing the boar Troynt (→Troit) (
Twrch Trwyth in Welsh): The second concerns Arthur's son Anir or Amr (
Amhar in Welsh) and his sepulchre: ==Germanus==