by Parliamentary forces. The castle was captured in 1643 by a group of Royalists who gained access by pretending to be Parliamentary soldiers. As the war turned against the King in the south-west, Parliamentary forces besieged the castle for four months in 1644, and once again the following year. The castle finally surrendered to Vice-Admiral William Batten in April 1646. It is uncertain why the castle, which was not easily defensible on the landward side, proved so difficult to take; the historian Peter Harrington has suggested that its low-lying position may have made it difficult for Parliament to bombard it from the sea. During the Interregnum, Portland Castle continued to be garrisoned and used a prison, with a unit of 103 men attached to it in 1651. It was used to defend the Portland Roads during the First Anglo-Dutch War of 1653, seeing action in a three-day long naval battle between English and Dutch forces. When Charles II returned to the throne in 1660, he reduced the garrison to its pre-war levels but repaired the fortifications in the light of the continuing Dutch threat; in 1676 the castle was equipped with 16 guns. Portland Castle continued in use through the 18th century, primarily protecting vessels against privateers, including merchant vessels carrying stone from the local Portland quarries. Reports in 1702 and 1715 complained about the dilapidated condition of the fortification – the sea had washed away of its foundations – and the number of artillery pieces was reduced to seven. By 1779, the castle had a caretaker garrison of three men and eight guns, and reportedly had not been repaired in the previous 30 years. During the Napoleonic Wars, the castle's guns were increased to comprise six 24-pounder, six 12-pounders and two 9-pounder guns (10.9 kg, 5.4 kg and 4.1 kg respectively), but the fortification remained in a poor condition overall. Following the final defeat of Napoleon, the castle was disarmed and leased to John Manning, a Portland churchman, who converted it from a fortress into a private house. John's son, Charles Manning, took over the house in 1834 and continued to develop it. Among the Mannings' work was the conversion of an older house alongside the main castle, which had once housed the master gunner, into a grander property, known today as the Captain's House. In the late 1840s, the Portland Roads were converted into an artificial harbour through