<P> King Arthur is a legendary British leader who, according to medieval histories and romances, led the defence of Britain against Saxon invaders in the late 5th and early 6th centuries AD . The details of Arthur's story are mainly composed of folklore and literary invention, and his historical existence is debated and disputed by modern historians . The sparse historical background of Arthur is gleaned from various sources, including the Annales Cambriae, the Historia Brittonum, and the writings of Gildas . Arthur's name also occurs in early poetic sources such as Y Gododdin . </P> <P> Arthur is a central figure in the legends making up the Matter of Britain . The legendary Arthur developed as a figure of international interest largely through the popularity of Geoffrey of Monmouth's fanciful and imaginative 12th - century Historia Regum Britanniae (History of the Kings of Britain). In some Welsh and Breton tales and poems that date from before this work, Arthur appears either as a great warrior defending Britain from human and supernatural enemies or as a magical figure of folklore, sometimes associated with the Welsh Otherworld, Annwn . How much of Geoffrey's Historia (completed in 1138) was adapted from such earlier sources, rather than invented by Geoffrey himself, is unknown . </P>

When did the story of king arthur take place