Tresco, Isles of Scilly
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A poorly sited castle
King Charles's Castle is a coastal artillery fort near the northern extremity of the island of Tresco. It is now in ruins and the site is administered by English Heritage. It was a semi-hexagonal structure to provide a wide field of fire and two-storey to give at least two tiers of guns. The domestic quarters for the garrison were at the rear.
After an abortive attempt in 1552 to build an artillery fort on St. Mary's, the remains of which are now known as Harry's Walls, Edward VI's engineers focused instead on strengthening Tresco.
Despite its name, the castle was built in 1554 during the reign of Edward VI to protect the Isles of Scilly against French attack. During the Civil War low earthwork defences were thrown up beyond the castle to protect it from landward attack. After the war it was replaced by Cromwell's Castle.
It was intended to protect the narrow strait leading past New Grimsby harbour and on towards St. Mary's, but proved to be badly sited to withstand attack or to fire on ships in the channel below. Its guns would have to point down at so steep an angle to hit ships in New Grimsby Channel that the cannonballs would have rolled out of the cannons before they fired.
It was garrisoned by the Royalists during the Civil War, but when the Parliamentarians took Tresco in 1651 they simply by-passed the castle by landing on the other side of the island. The castle seems to have been partially dismantled to provide stone for Cromwell's Castle which was built on lower ground. The castle was partially excavated in 1954, uncovering coins, pottery and a buckle.
Cornish Castles Isles of Scilly Tresco Oliver's Battery English Heritage in Cornwall