Built as a result of the 1859 Royal Commission by Lord Palmerston to prevent a French land attack on the Portsmouth dockyard only 8 kilometres away, because the older Hilsea Lines at the bottom of the ridge were considered insufficient.

The Council, with assistance of volunteers from the Palmerston Forts Society, restored it at a cost of £3–4 million, and it opened to the public in 1994, becoming part of the Royal Armouries in 1995.

It houses their collection of artillery, including: The fort covers around 19 acres (77,000 m2) and is open all year round, with no charges except for some special events.

Live firing demonstrations are held every day, costumed guides, video presentations, and visitors are able to explore the tunnels that run below the fort connecting the magazines with gun emplacements.

There are displays demonstrating the living and working conditions of the soldiers who defended the fort, and views over Portsmouth, the Solent, Hayling Island and Gosport, with the Isle of Wight beyond.