Cromwells Castle

Listed building

What is recorded here

Cromwell's Castle was built in 1651–52 after Parliament retook the Isles of Scilly, guarding New Grimsby harbour against hostile ships. Its round gun tower and the six-gun platform added around 1739 preserve two different answers to changing naval threats.

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Who built and held it

Sir Robert Blake ordered the tower after Parliamentary forces recovered Scilly from Royalist control at the end of the Civil War. Builders reused stone from the earlier King Charles's Castle higher on the hillside, placing the new guns much closer to the water.

Attack, change and use

The tower watched the narrow entrance to New Grimsby harbour against Dutch, Irish and Royalist vessels. During the War of Jenkins' Ear around 1739, master gunner Abraham Tovey added a low platform for six guns, although the fort soon fell out of regular use.

What survives

The circular tower rises above a basement and former living space to a roof gun position, with immensely thick stone walls. Beside it, the eighteenth-century battery still faces across the channel that both phases were intended to close.

Why it mattered

This is a rare stone fort built during the period when England had no king. Its move downhill from an older castle and its later open battery show how artillery defence changed when controlling ships, rather than commanding land, became the chief task.