The text of this letter can be found in old English in Wulfstan's homilies.

Besides sacred legends, others exist of a worldly nature, such as the supposed letter from Alexander to Aristotle, the Wonders of the East, and the Story of Apollonius of Tyre.

The first two, of course, formed part of the great Alexander cycle, while the latter supplied the theme for Pericles of Tyre.
With the Norman Conquest, French became the literary language of England, and modern romance was born.

Romance cycles on "the matter of France" or Legends of Charlemagne, and on "the matter of Britain" or Legends of Arthur, became popular, and Geoffrey of Monmouth freely made use of his imagination to fill up the early history of Britain, for his so-called history is in reality a prose romance, whence later writers drew themes for many a tale.
Walter Map, born on the border of Wales in 1137, is credited with the no longer extant Latin prose romance of Lancelot du Lac, which included the Quest of the Holy Grail and the Death of Arthur.

Besides Wace's Brut, we have that of Layamon, and both poets not only explain how Britain's name is derived from Brut,--a member of Priam's family and refugee from Troy,--but go on to give the history of other early kings of Britain, including Arthur.