The panegyrist of Philip Augustus asserts that John’s sudden dash into the lands south of Périgord was prompted by dread of Philip, who, “being desirous to meet him” in the field, had hurried to the Poitevin border, and was preparing to cut him off from his fleet. The same writer, however, owns almost in the same breath that “no one knows, ever has known, or ever will know, the way of a serpent, of a ship on the deep, of a feather in the wind, or of a deceiver” such as John; and that Philip dared neither attempt to follow him nor await his return, but hurried back--after burning the rural districts of Poitou--to protect his own interests in Flanders.[881] John’s erratic movements had probably a double purpose: to baffle Philip, and to ascertain the extent of his own resources in the south. Of more real importance than these tentative excursions was a negotiation which he had set on foot with the house of Lusignan, whose alliance and allegiance he proposed to regain by giving the infant Joan, his eldest daughter by Isabel of Angoulême, in marriage to young Hugh of La Marche, as compensation for the loss of Isabel herself. The first preliminary was a truce with the counts of La Marche and Eu; and it was probably this truce which enabled John to pass unmolested through La Marche on his way to and from La Souterraine. The third Lusignan brother, Geoffrey, seems not to have been included in the truce; and when it expired no terms of peace had been agreed upon. “We therefore”--so wrote John to his representatives in England--“on the Friday next before Pentecost {May 16} transported ourself and our army to Geoffrey’s castle of Mervant; and although many believed it impregnable by assault, yet on Whitsun Eve {May 17}, by one assault lasting from daybreak to the hour of prime, we took it by force. On Whitsunday {May 18} we laid siege to another of Geoffrey’s castles, Vouvant, in which was he himself with his two sons; and when we had plied our slings against it continually for three days {May 20}, so that its fall was imminent, the count of La Marche came to us and caused the said Geoffrey to surrender himself to our mercy, with his two sons, his castle, and all that was in it.” Another of Geoffrey’s castles, Montcontour, which lay farther east, close to the Angevin border, was at the same time besieged by Louis of France. The French king seems to have discovered the negotiations of the Lusignans with his rival, and to have been so much alarmed at the prospect of a reconciliation which would deprive him of his best helpers in Aquitaine that he tried to prevent it by offering a son of his own as bridegroom for little Joan; but Joan’s father was too wary to take the French bait. On learning that Louis was at Montcontour, “we,” says John, “at once turned thitherward to meet him; so that on Trinity Sunday {May 25} we were at Parthenay, where the count of La Marche and the count of Eu came to us with the said Geoffrey