King Arthur, possibly a figure in the British (Welsh) resistance against invading Saxons, Angles and Picts
victory over the Saxons at Battle of Mount Badon (Mons Badonicus) (c. 500-518)
death of Arthur, Battle of Camlann (c. 537-538), near Glastonbury
Sources:
Literary treatment:
Kulhwch and Olwen (c. 1100), Welsh prose romance (part of the Mabinogion), one of the earliest Arthurian romances
Wace, Roman de Brut (Romance of Brutus) (1155), first mention of the Round Table
Chrétien de Troyes (fl. 1165-1180), Arthurian romances, Lancelot, Yvain, Perceval, major influence on subsequent Arthurian literature
Robert de Boron (early 13th century), French poet, trilogy of poems (Joseph d'Arimathe, Merlin, Perceval), story of the Grail
Layamon's Brut (c. 1189-1205), based on Wace's and Geoffrey of Monmouth's work; first account in English of Arthurian stories
Vulgate Cycle (completed before 1240), French prose renditions of earlier, poetic versions of the Arthurian legends; the cycle includes a prose Lancelot, Merlin, and other stories
Alliterative Morte Arthure (Death of Arthur)(c. 1370-1380), alliterative verse romance, part of movement known as Alliterative Revival
Sir Thomas Malory (c. 1405-1471), Morte D'Arthur (Death of Arthur) (c. 1469-70) (printed by William Caxton in 1485), English prose