In 1214, they fulfilled their vassal duties by joining the Breton levy to support the war effort of the French against the English.

[3] A record from October 14, 1251, kept at the Departmental Archives of Loire-Atlantique, states that Olivier 1’s half-brothers, Eudes de Pont and Guillaume de Fresnay, both knights, entered into an agreement of mutual assistance with the Duke John 1, to secure the lands of Pontchâteau for themselves which Olivier 1 inherited as Constance’ eldest son.

To defend himself against theses encroachments of the ducal authority, Olivier de Clisson appealed to the king of France for justice.

He found an ally in Alain d'Avaugour, lord of Mayenne and Dinan, heir to the counts of Rennes and rival of the Dukes of Brittany.

The ruling ordered the return of the fiefs seized by the Duke to their former holders balanced against paying retributory fines.

Olivier I could not demand compensation from the Duke for his destroyed castle, he did recover Maison de la Verrerie.