Ambrosius Aurelianus as a war leader of the Romano-British who won an important battle in the 5th century, according to a 6th-century British monk best known for his scathing religious polemic which recounts the history of the Britons before and during what? 
Ambrosius Aurelianus: Ambrosius Aurelianus (Welsh: "Emrys Wledig" ; Anglicised as Ambrose Aurelian and called Aurelius Ambrosius in the "Historia Regum Britanniae" and elsewhere) was a war leader of the Romano-British who won an important battle against the Anglo-Saxons in the 5th century, according to Gildas. Gildas: Gildas (Breton: "Gweltaz", c. 500–570) — also known as Gildas the Wise or Gildas Sapiens — was a 6th-century British monk best known for his scathing religious polemic "De Excidio et Conquestu Britanniae", which recounts the history of the Britons before and during the coming of the Saxons.
the coming of the Saxons