The Chroniclers
c. 540 – c. 1200
Gildas, Nennius, Wace and Layamon — the line that built Arthur as history, and quietly gave the game away.
Four writers across six centuries, each handing the next a slightly larger Arthur.
Gildas (On the Ruin of Britain, c. 540) is the one witness who might have known. He describes the British victory at Mount Badon — the battle later tradition makes Arthur's greatest — and does not name him. The historical Arthur is missing from the only source close to the events.
Nennius (History of the Britons, c. 830) supplies the first Arthur we have: a war-leader, not a king, credited with twelve battles and, at Badon, nine hundred and forty men killed by his own hand. Legitimacy here is not election or descent. It is simply winning.
Wace (Roman de Brut, 1155) turns Geoffrey into French verse and, in the process, invents the Round Table — explicitly as a piece of engineering against precedence, so that no man at Arthur's court could claim to sit above another. He is also the first to record the Breton hope that Arthur will return.
Layamon (Brut, c. 1200) Englishes Wace and lets the marvellous back in: the elf-queen Argante bears the wounded king away to Avalon with balm for his wounds, and the Britons believe he will come again.
The strongest case for
The chroniclers turned a possible sixth-century war-leader into a usable past — and Wace and Layamon handed the romancers two load-bearing devices, the Round Table and the deferred return, before a single courtly romance had been written. Without them there is nothing for Chrétien to decorate.
The standard objection
This is the seam where fiction is sold as history, and Gildas's silence is the standing rebuke: the more confidently a chronicler names Arthur, the further he stands from the events. Nennius writes three centuries after Badon; Geoffrey six. The line does not get more reliable as it gets more detailed. It gets less.
Gildas is held as a search source only: this portal publishes Nennius from a better text than the collected volume that carries him.
How it maps
The root of the source of rule (legitimacy as conquest), of the once-and-future return (Wace's hope, Layamon's Argante), and — through Nennius's battle-roll — of the fellowship. Gildas and Nennius come before Geoffrey; Wace and Layamon carry him into the vernaculars and toward romance.
Validated quotations
“their chairs should be high alike, their service equal, and none before or after his comrade. Thus no man could boast that he was exalted above his fellow, for all alike were gathered round the board”
Roman de Brut, Wace, Roman de Brut · read in place“The twelfth was a most severe contest, when Arthur penetrated to the hill of Badon. In this engagement, nine hundred and forty fell by his hand alone, no one but the Lord affording him assistance”
Historia Brittonum, Nennius §56 · read in place“he would fare into Avalon, into the island, to Argante the fair, for she would with balm heal his wounds,--and when he were all whole, he would soon come to them. This believed the Britons, that he will thus come”
Layamon's Brut, Layamon, Brut · read in place