In 1642 the English Civil War broke out between the Royalist supporters of Charles I and the supporters of Parliament. Banbury Castle was initially held by William Fiennes, the son of Richard, for Parliament and the castle was hastily refortified. After the battle of Edgehill, Charles marched south and forced the surrender of the castle and its stock of 1,500 firearms. The fortifications were strengthened and in 1644 the castle was besieged again, this time by Parliamentary forces under the command of William Fiennes. The royal governor, the 18-year-old William Compton, held out between July and October, when Compton's brother, James, relieved the siege. In November, Charles I dined in the castle. In January 1646 Sir Edward Whalley placed the castle under siege again with a force of 3,000 men; the Royalist cause was collapsing, and in May Compton and his force of 300 men surrendered.