It is a Palmerston Fort, constructed in the 1860s.

It is one of the many Palmerston Forts built on the island to protect it in response to a perceived French invasion.

Large scale permanent fortifications built in peace time (such as the Palmerston Forts) were seen as a waste of money.

He also proposed to build a sea fort in the bay, along the lines of Britain's Palmerston Forts, though this was never carried out.

The Palmerston Forts around the north east of England include:

In 1867, the construction of the Palmerston Fort on St Catherine's Island began.

Jarvois went on to oversee the design of the resulting new fortications which became known as the Palmerston Forts.

These were generally known as Palmerston Forts.

The Palmerston Fort is constructed of Granite and Limestone.

These forts became known as the Palmerston Forts.