As a result of his new prominence in the Montfortist camp, his lands in French controlled Brittany were confiscated in October 1344 and given to William the Binder.

Afture the capture of John de Montfort, Amaury was appointed regent of Brittany and tutor to the young Duke.

Chroniclers, state that two captured Breton knights were to be killed by Luis de la Cerda at the base of the city's rampart.

[6] De Clisson was involved and apparently killed in the Battle of La Roche-Derrien which was fought on 20 June 1347 during the night between Anglo-Breton and Franco-Breton forces.

Approximately 4,000–5,000 French, Breton and Genoese mercenaries laid siege to the town of La Roche-Derrien in the hope of luring the Anglo-Bretons into an open pitched battle.