He was even careful, by his last will, to declare his brother John heir to all his dominions; whether, that he now thought Arthur, who was only twelve years of age, incapable of asserting his claim against John's faction, or was influenced by Eleanor, the queen mother, who hated Constantia, mother of the young duke, and who dreaded the credit which that princess would naturally acquire if her son should mount the throne.

The authority of a testament was great in that age, even where the succession of a kingdom was concerned; and John had reason to hope, that this title, joined to his plausible right in other respects, would insure him the succession.

But the idea of representation seems to have made, at this time, greater progress in France than in England; the barons of the transmarine provinces Anjou, Maine, and Touraine, immediately declared in favor of Arthur's title, and applied for assistance to the French monarch as their superior lord.
Philip, who desired only an occasion to embarrass John, and dismember his dominions, embraced the cause of the young duke of Brittany, took him under his protection, and sent him to Paris to be educated along with his own son Lewis.

In this emergency, John hastened to establish his authority in the chief members of the monarchy; and after sending Eleanor into Poictou and Guienne, where her right was incontestable, and was readily acknowledged, he hurried to Rouen, and having secured the duchy of Normandy, he passed over, without loss of time, to England.
Hubert, archbishop of Canterbury, William Mareschal, earl of Strigul, who also passes by the name of earl of Pembroke, and Geoffrey Fitz-Peter, the justiciary, the three most favored ministers of the late king, were already engaged on his side; and the submission or acquiescence of all the other barons put him, without opposition, in possession of the throne.
The king soon returned to France, in order to conduct the war against Philip, and to recover the revolted provinces from his nephew Arthur.
The alliances which Richard had formed with the earl of Flanders, and other potent French princes, though they had not been very effectual, still subsisted, and enabled John to defend himself against all the efforts of his enemy.

In an action between the French and Flemings, the elect bishop of Cambray was taken prisoner by the former; and when the cardinal of Capua claimed his liberty, Philip, instead of complying, reproached him with the weak efforts which he had employed in favor of the bishop of Beauvais, who was in a like condition.