Old Blockhouse

Substantial remains of a small 16th century gun tower protecting Old Grimsby harbour, vigorously defended during the Civil War.

The Block House formed part of a series of forts built on the islands during the reigns of Edward VI and Mary I, and followed the attempt to build a large artillery fort, known as Harry’s Walls, on St Mary’s.

In fact, the blockhouse did not see action until the 17th century, during the English Civil War. In 1651 a Royalist garrison was defending the islands against attack by a Parliamentarian fleet commanded by the famous Admiral Blake.

Blake attacked Tresco first, capturing its fortifications without difficulty, and then used the island as a base to assault the main Royalist stronghold at Star Castle on St Mary’s. Though vigorously defended, the Old Blockhouse clearly proved of little value against the longer-range guns of Blake’s ships.

It was replaced afterwards by the much stronger gun fort, called Cromwell’s Castle, on the other side of the island, though it was still considered serviceable in the 18th century.