During the 16th and 17th centuries the castle continued to be maintained and modified; the seaward half of the castle was turned into a solid gun platform and additional accommodation was built for the fort's gunners. A bulwark was built on the east side of the castle and an additional gun battery was placed on the town's quay, just to the west. For most of the English Civil War of the 1640s it was held by Parliament; following the Restoration, it was refortified by Charles II in the 1670s.