On 11 June 1258, at Oxford, a council of barons resolved to rule the country in conjunction with King Henry III, who was deemed to be mentally incapable. This was prompted by a variety of reasons. The previous year's weather had been bad, with poor harvests and "murrain. The ordinary people of England were also suffering greatly from the expenses of war. Before the council, another was formed, which drew up the Provisions of "Oxford. Henry's foreign advisers were extremely unpopular; indeed it was thought they were favoured above the English and their wealth was much disapproved of. Feeling was such that they then decamped; their land and castles were immediately confiscated and distributed. However, the council began internecine squabbling.
Dictionary of Medieval Terms and Phrases. Christopher Coredon with Ann Williams.