Fort Nelson sits high up on peaceful Portsdown, overlooking the Royal Naval Dockyards of Portsmouth. As one of a circle of forts, collectively known today as the 'Palmerston' forts (the Prime Minister at the time of their conception) Fort Nelson was built during the 1860s to defend the dockyards against the potential threat of a French invasion.
Using the same polygonal plan first employed in the forts of the 'Gosport Advanced Line' some years earlier, Fort Nelson comprises six brick elevations shaped into an arrowhead, the entire perimeter being surrounded by a deep dry moat. Rising up from the walls, and running roughly parallel, are a series of turf covered ramparts, beneath which are a series of underground passageways. These tunnels enabled members of the garrison to move around Fort Nelson freely, without being exposed to attack. The top of the ramparts provided space, and additional height, for Fort Nelson's heavy armament, as well as a number of cartridge and shell stores.
Along the southern elevation, at the concave angle where the two walls meet, is a large triangular building called a Redan. With its apex pointing due south, this building accommodated most of the garrison, and differs from earlier structures such as Fort Brockhurst and Newhaven Fort, whose garrisons would have been accommodated in arched casemates built directly under the ramparts.
Moving northwards along the west and east elevations towards the 'shoulders' of the polygon are two projections called demi-caponiers. These were built deep into the moat and allowed fire to be directed back along the moat in the event of the enemy trying to breach the east and west walls. Further north again to the apex of the polygon can be found a double-sided caponier, which similarly allowed small arms fire to be directed along the northern walls back in the direction of the demi-caponiers. Set deep within the ramparts behind each of the caponiers are underground mortar batteries, each holding 3 x 13inch (325mm) cast iron mortars capable of throwing a projectile some 3,000 yards with remarkable accuracy. The central area behind the ramparts was taken up by a substantial parade ground.
As history shows, the perceived invasion never materialised and life at Fort Nelson remained largely uneventful until the outbreak of the Second World War. By this time it had been realised that these old Victorian forts could provide valuable anti-aircraft cover against enemy bombers. In 1938, just prior to the outbreak of hostilities, ten enormous anti-aircraft ammunition stores were constructed covering virtually the entire parade ground, two of which remain today. Following the war, Fort Nelson was largely abandoned, until its future was secured when Hampshire Council purchased it in 1979. Viewed as a potential heritage site Fort Nelson opened its doors to the public in 1984, the first time in over one hundred years.
In 1988 the Royal Armouries, who were looking for an appropriate site to house their ever-increasing artillery collection, leased Frot Nelson from Hampshire Council and a substantial renovation program was begun. In 1995 Fort Nelson opened its doors for the first time as a fully established artillery museum. Today visitors can freely explore all areas of Fort Nelson, as well as examine artillery pieces on both the parade ground and in the exhibition galleries. On special event days, members of the Portsdown Artillery Volunteers demonstrate the firing of selected pieces, in full authentic regalia.