 It was built by the Royalists in 1651 to defend the hill, because during the siege in 1646 Parliamentary forces had positioned their artillery on the hill and had been able to severely damage the city's walls.During the final stages of the Battle of Worcester, fought on 3 September 1651, the last battle of the war and a Parliamentary victory, the Royalists retreat turned into a rout in which Parliamentarian and Royalist forces intermingled and skirmished up to and into the city.The Royalist position became untenable when the Essex militia stormed and captured Fort Royal, turning the Royalist guns to fire on Worcester.