His chief scruple was with regard to the fidelity which he might expect from the English barons in their new engagements, and the danger of intrusting his son and heir into the hands of men who might, on any caprice or necessity, make peace with their native sovereign, by sacrificing a pledge of so much value.

He therefore exacted from the barons twenty-five hostages of the most noble birth in the kingdom; and having obtained this security, he sent over first a small army to the relief of the confederates; then more numerous forces, which arrived with Lewis himself at their head.
The first effect of the young prince's appearance in England was the desertion of John's foreign troops, who, being mostly levied in Flanders, and other provinces of France, refused to serve against the heir of their monarchy.

The Gascons and Poictevins alone, who were still John's subjects, adhered to his cause; but they were too weak to maintain that superiority in the field which they had hitherto supported against the confederated barons.

Many considerable noblemen deserted John's party, the earls of Salisbury, Arundel, Warrenne, Oxford, Albemarle, and William Mareschal the younger: his castles fell daily into the hands of the enemy; Dover was the only place which, from the valor and fidelity of Hubert de Burgh, the governor, made resistance to the progress of Lewis; and the barons had the melancholy prospect of finally succeeding in their purpose, and of escaping the tyranny of their own king, by imposing on themselves and the nation a foreign yoke.
But this union was of short duration between the French and English nobles; and the imprudence of Lewis, who on every occasion showed too visible a preference to the former, increased that jealousy which it was so natural for the latter to entertain in their present situation.

The viscount of Melun, too, it is said, one of his courtiers, fell sick at London; and finding the approaches of death, he sent for some of his friends among the English barons, and warning them of their danger, revealed Lewis's secret intentions of exterminating them and their families as traitors to their prince, and of bestowing their estates and dignities on his native subjects, in whose fidelity he could more reasonably place confidence.