King Charles' Castle

King Charles's Castle is a ruined artillery fort overlooking New Grimsby harbour on the island of Tresco in the Isles of Scilly. Built between 1548 and 1551 to protect the islands from French attack, it would have held a battery of guns and an accompanying garrison, designed to prevent enemy vessels from entering the harbour. The castle is polygonal in design, constructed from granite stone, with the gun battery at the front, and a dining room, kitchen and living accommodation at the rear. An additional defensive earthwork was constructed around it during the 17th century. The design of the castle is unusual for the period, and is only seen elsewhere in blockhouses along the River Thames. The castle's design was unsatisfactory, as its guns could not be angled so to fire down into the harbour, and its defences were considered vulnerable to attack. To mitigate this, an additional blockhouse was probably constructed below, closer to the water, but eventually a new fortification, the Star Castle, was built instead on the neighbouring island of St Mary's, which became the main fort in the Scilly Isles. In the aftermath of the English Civil War, the Scilly Isles were held by the Royalist sympathisers of King Charles I, who gave the castle its current name. The islands were then attacked by a Parliamentary force led by Sir Robert Blake in 1651, who landed on Tresco but bypassed the fort as he took the island. Its Royalist defenders blew up parts of the castle as they left, and some of its stone appears to have been used to build the newer Cromwell's Castle by the harbour. Although King Charles's Castle was being used to house soldiers in 1660, by the 18th century it was described as ruinous. After 1922, the castle passed into the guardianship of the Ministry of Works, and archaeological excavations were carried out in 1954. In the 21st century the site is controlled by English Heritage and is open to visitors. It is protected under UK law as a scheduled monument and a Grade II* listed building.