The Picts were a group of Late Iron Age and Early Mediaeval Celtic people living in ancient eastern and northern Scotland. There is an association with the geographical distribution of brochs, Brythonic place name elements, and Pictish stones. Picts are recorded from before the Roman conquest of Britain until the 10th century, when they merged with the Gaels. They lived to the north of the rivers Forth and Clyde, and spoke the extinct Pictish language, thought to have been related to the Brythonic languages spoken by the Britons to the south. They are assumed to have been the descendants of the Caledonii and other tribes named by Roman historians or found on the world map of Ptolemy. Pictland, also known as Pictavia, gradually merged with the Gaelic kingdom of Dál Riata to form the Kingdom of Alba (Scotland). Alba expanded, absorbing the Brythonic kingdom of Strathclyde and Bernician Lothian, and by the 11th century the Pictish identity had been subsumed into the "Scots" amalgamation of peoples.

King Arthur is a legendary British leader of the late 5th and early 6th centuries, who, according to medieval histories and romances, led the defence of Britain against Saxon invaders in the early 6th century. 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.

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). Some Welsh and Breton tales and poems relating the story of Arthur date from earlier than this work; in these works, 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.