In answer to every advance which the king made towards peace, Philip still insisted that he should resign all his transmarine dominions to his nephew and rest contented with the kingdom of England; when an event happened, which seemed to turn the scales in favor of John, and to give him a decisive superiority over his enemies.
Young Arthur, fond of military renown, had broken into Poictou at the head of a small army; and passing near Mirebeau, he heard that his grandmother, Queen Eleanor, who had always opposed his interests, was lodged in that place and was protected by a weak garrison and ruinous fortifications.

He immediately determined to lay siege to the fortress, and make himself master of her person; but John, roused from his indolence by so pressing an occasion, collected an army of English and Brabancons, and advanced from Normandy with hasty marches to the relief of the queen mother.

He fell on Arthur's camp, before that prince was aware of the danger; dispersed his army; took him prisoner together with the count de la Marche, Geoffrey de Lusignan, and the most considerable of the revolted barons, and returned in triumph to Normandy.

Philip, who was lying before Arques, in that duchy, raised the siege and retired upon his approach.

The greater part of the prisoners were sent over to England, but Arthur was shut up in the castle of Falaise.
The king had here a conference with his nephew; represented to him the folly of his pretensions; and required him to renounce the French alliance, which had encouraged him to live in a state of enmity with all his family; but the brave, though imprudent youth, rendered more haughty from misfortunes, maintained the justice of his cause; asserted his claim, not only to the French provinces, but to the crown of England; and, in his turn, required the king to restore the son of his elder brother to the possession of his inheritance; John, sensible, from these symptoms of spirit, that the young prince, though now a prisoner, might hereafter prove a dangerous enemy, determined to prevent all future peril by despatching his nephew; and Arthur was never more heard of.
The circumstances which attended this deed of darkness were, no doubt, carefully concealed by the actors, and are variously related by historians; but the most probable account is as follows: The king, it is said, first proposed to William de la Braye, one of his servants, to despatch Arthur; but William replied that he was a gentleman, not a hangman; and he positively refused compliance.