 Henry III 's reign was in crisis in 1258 . He had recently suffered defeat in Wales , there were agricultural problems leading to a famine , and relations with the pope were worsening . Discontent amongst England 's magnates led Henry to promise reform , but under continued pressure his authority disintegrated . A royal council of fifteen magnates was formed in June that year , and the rule of the country transferred from the king to the council . With foreign help Henry 's reign was restored in 1261 as the council were reluctant to start a civil war . Simon de Montfort , Earl of Leicester , raised a rebellion . In 1264 civil war broke out between those loyal to the king and the baronial forces led by de Montfort . 
