Otho joined his brother Thomas in Edward III's military expedition to Normandy in 1346 and fought at the Battle of Caen. There the Constable of France surrendered himself to his brother who sold him to the King. Back in England the Constable was given to Otho to guard until he could be ransomed but Otho allowed his prisoner too much freedom (by allowing him to cross to France on parole) and was heavily censured as a result.