The legate, to show his impartiality, laid at the same time the kingdom of France and the duchy of Normandy under an interdict; and the two kings found themselves obliged to make an exchange of these military prelates.
{1200.} Nothing enabled the king to bring this war to a happy issue so much as the selfish, intriguing character of Philip, who acted, in the provinces that had declared for Arthur, without any regard to the interests of that prince.

Constantia, seized with a violent jealousy that he intended to usurp the entire dominion of them, found means to carry off her son secretly from Paris: she put him into the hands of his uncle; restored the provinces which had adhered to the young prince; and made him do homage for the duchy of Brittany, which was regarded as a rere-fief of Normandy.

From this incident, Philip saw that he could not hope to make any progress against John; and being threatened with an interdict on account of his irregular divorce from Ingelburga, the Danish princess whom he had espoused, he became desirous of concluding a peace with England.

After some fruitless conferences, the terms were at last adjusted; and the two monarchy seemed in this treaty to have an intention, besides ending the present quarrel, of preventing all future causes of discord, and of obviating every controversy which could hereafter arise between them.

They adjusted the limits of all their territories; mutually secured the interests of their vassals, and, to render the union more durable, John gave his niece, Blanche of Castile, in marriage to Prince Lewis, Philip's eldest son, and with her the baronies of Issoudun and Gracai, and other fiefs in Berri.