Robert thereafter followed King Edward III in his campaigns, including command of the Anglo-Flemish army at the Battle of Saint-Omer in 1340. He ultimately succumbed to dysentery after being wounded while retreating from the city of Vannes in November 1342, during the War of the Breton Succession. He was originally buried in the church in Blackfriars, London, though his grave is now in St. Paul's Cathedral.