Complex sentence: The British guards were shocked by Domery's appetite, and agreed to place him on double rations; this was insufficient and his rations were increased until he was granted the rations of ten men each day.
Split into simpler sentences: The British guards were shocked by Domery's appetite, and agreed to place him on double rations. These were insufficient, and his rations were increased until eventually he was granted the rations of ten men each day.