 King John died in October , and in December Louis besieged Berkhamsted Castle . The prince deployed his siege engines , probably trebuchets , and attacked the castle repeatedly for twenty days , throwing what chroniclers termed innumerable " damnable stones " at the defenders . During the 13th century , a set of earthworks were built around the outside of the walls , which may have been the firing platforms for these trebuchets . Having put up a strong defence , the garrison was allowed to surrender and to leave with their weapons and armour . When the forces loyal to the young Henry III defeated the rebels the following year , the castle was returned to royal hands . 
