Britain is the kingdom at the center of Arthur’s rise to power, his duties as ruler, and his claim to sovereignty beyond the island. Its political order is first secured through the public recognition of Arthur as king; later, the Roman demand for tribute turns that sovereignty into an imperial dispute, while the story also shows how rebellion can threaten the realm from within.

Kingship and the Realm

Britain’s succession is unsettled after Uther Pendragon’s death. Before dying, Uther publicly blesses Arthur as his heir and commands the barons to accept his claim. His death does not immediately resolve the question: powerful lords gather strength, and many aspire to the crown. The archbishop of Canterbury, acting on Merlin’s advice, summons the realm’s lords to London, where the sword in the stone becomes a public test of rightful kingship.

Arthur alone can draw the sword. When the assembled people acclaim him at Pentecost, he forgives those who delayed his recognition, offers the sword at the altar, and is crowned. He swears to rule with justice, then restores lands taken from their rightful holders during the unsettled period after Uther’s death. His authority is thus shown not only through a miraculous sign, but through public consent and the repair of political wrongs.

Governance and Obligations

After his coronation, Arthur assigns offices to support the administration and defense of Britain. Sir Kay becomes seneschal, Sir Bawdwin of Britain constable, Sir Ulfius chamberlain, and Sir Brastias is charged with guarding the northern approaches. Arthur later extends his power across the north, Scotland, and Wales, bringing territories that had resisted him under his rule.

The king’s authority is accompanied by a code imposed on the Knights of the Round Table. They swear to avoid outrage and murder, reject treason and cruelty, show mercy to those who ask it, and aid ladies and gentlewomen. They are also forbidden to fight in wrongful causes for legal claims or worldly gain. The oath is renewed each year at Pentecost, making the defense of the realm inseparable from recurring public obligations among its knights.

Sovereignty and Rome

The question of Britain’s independence becomes explicit when twelve aged Roman ambassadors arrive at Arthur’s court bearing olive branches. They demand tribute on behalf of Emperor Lucius, claiming that Britain owes Rome the payment made by earlier rulers and threatening war if Arthur refuses. Arthur prevents his knights from harming the messengers, orders that they receive good lodging and provisions, and consults his lords before answering. The scene sets diplomatic restraint alongside a refusal to submit.

Arthur grounds his position in a rival account of political right: he invokes the British kings Belinus and Brennius, who held the empire, and Constantine, son of Queen Helena, as evidence that his own line may claim imperial sovereignty. His answer rejects any tribute owed to an earthly prince and declares an intention to march on Rome and take possession of the empire. The allied rulers and lords pledge military support; among them, the King of Scotland promises twenty thousand men at his own expense. Arthur sends the ambassadors back with gifts and pays their expenses, maintaining the obligations of royal honor even as he rejects their demand.

The Realm in the King’s Absence

Before departing on the Roman campaign, Arthur holds a parliament at York and orders the kingdom’s navy to be ready at Sandwich within fifteen days. He entrusts governance to Sir Bawdwin of Britain and Sir Constantine, Cador’s son, and leaves Queen Guenever and the realm in their care. In public, he names Constantine as his heir should he die on the expedition.

The arrangement makes the vulnerability of Britain visible: its stability depends on delegated authority while its king is abroad. Elsewhere, the account of Mordred’s presumption—taking the title of king and seeking to marry his uncle’s wife—shows the opposite course: a claim to rule that breaks rather than preserves the established order. Britain is therefore represented both as a realm secured by recognized succession and shared duties, and as a kingdom exposed when those loyalties fail.