The castle became the property of the Crown and improvements were made to its defences. In 1399 Richard II is supposed to have hidden treasure somewhere within Beeston Castle before being captured by the future Henry IV. Some treasure was discovered and handed over to Henry but some believe that there is more treasure to be found and the well is suspected to be the most likely location.
During the English Civil war the castle was commanded by a group of Parliamentarians who believed the castle could not be captured. But several skilled Royalist managed to scale the sheer cliffs on the northern side and took the castle by surprise. The Royalists held the castle until the end of the war at which point the Parliamentarians took control of it and ordered that it should be destroyed, and it has remained in a ruined state ever since.