From the outside it reads as an ellipse; step inside and the walls resolve into a perfect circle. That contradiction is not accidental. It is a deliberate feature of a distinctive class of coastal fortification, and in this case the structure is remarkably complete.

The tower was built between 1811 and 1814, a period when Britain was investing heavily in the defence of its coastline against Napoleonic threat. Standing roughly twelve metres high with an internal diameter of just under nine metres, it was designed to serve multiple purposes within a tight footprint. The ground floor housed a magazine for storing powder and shot, below which a basement water tank was cut into the structure. Above the magazine, reached by a doorway set into the north face at first-floor level, lay living quarters for whatever small garrison was posted there. Mural stairs, built into the thickness of the wall itself, lead up to a circular gun emplacement on the roof, measuring just over seven and a half metres across. That emplacement was positioned eccentrically, offset from the tower's centre so that the parapet on the seaward side would be deeper and offer better cover. The single gun mounted there rotated through a full 360 degrees on an iron traversing platform, and parts of that platform, along with the original 24-pounder cannon, are still present on site. A 24-pounder, so named for the weight of the iron ball it fired, was a substantial piece of ordnance capable of engaging vessels at considerable range, making even a single-gun installation a credible deterrent in a sheltered inlet like this one.