According to one account Charles begged for his life and promised to leave France forever, but the Bascon de Mareuil and Rabigot Dury fell upon him with four other troopers and stabbed him to death.
After a brief attempt to negotiate with John II he withdrew to the Cotentin where he set up headquarters at Cherbourg and proclaimed himself his brother's lieutenant in France.
Though the region had a long tradition of opposition to the French Crown the local nobility were reluctant to throw in their support as the Navarrese caused appeared doomed to fail.
However Philip knew that the resources of Navarre alone could never be enough to sustain a war against France and by the end of April he had sent to emissaries to England to seek an alliance.
Though initially sceptical by 4 May the English government had decided to divert Henry, Duke of Lancaster's planned invasion of Brittany to Normandy.
They had failed to relieve Evreux, but brought back considerable booty making the short campaign a profitable venture for the participants.
The raid also caused John II to be caught in a pointless siege of Breteuil instead of focusing on the threatening events taking place to the south.
The rest of the year Philip spent in England together with his Chancellor Thomas de Ladit to settle the terms of his alliance with Edward III.
The capture of John II in the Battle of Poitiers on 17 September threw the French government, now headed by the Dauphin, into disarray.
When the heirless Norman nobleman Godfrey of Harcourt fell in battle against the French in November 1356 Philip had taken possession of his castle, Saint-Sauveur-le-Vicomte, one of strongest and most valuable in the region.
Philip had attempted to persuade Edward that the release of his brother Charles should be one of the conditions for a truce with France, but met only evasions.
9 November 1357 Charles of Navarre escaped from his prison at Arleux, three weeks later he was received as a hero returned by a Paris increasingly hostile to the Dauphin's government.
This sped up the proceedings considerably and the kings agreed to a draft treaty, which among other things, provided that Philip of Navarre should be restored to all that he had held in France before the outbreak of the civil war.
However, by July the Dauphin had gained the advantage in the power struggle; he had the support of the French aristocracy, the Parisians, provoked by the presence of English and Navarrese guards within the city, were also increasingly sympathetic to his cause.
Composed mainly of Englishmen the army also included such veteran captains as Robert Knolles and Hugh Calveley and Philip's marshal John Fotheringhay.
Before Philip could arrive the mood of the city had completely turned against the King of Navarre who had been forced to barricade himself in Saint-Denis with his guards.
He instead led his army into western Champagne where he sustained himself for six weeks while evading the counterattacks of the Constable and Admiral of France, returning to Normandy in early June having achieved little of lasting value.