Work on The Sea Forts began in 1860 but suffered many delays. By the time they were completed, two decades later, the threat of war with France had evaporated. Military strategy and weapons technology had also moved forward, rendering the new defences obsolete.
Arguably, they may have discourage hostilities 20 years earlier if France’s self-styled emperor, Napoleon III had indeed intended to go to war. But public opinion now saw the exercise as an enormous governmental folly. Fairly or not, they became known as “Palmerston Follies”, after Lord Palmerston, the prime minister whose government had commissioned them.
The nickname endured for over a century, until the 1990s brought a change of attitude as leisure and tourism took on greater importance to the local economy. The former “follies” began to be seen as part of Portsmouth’s historical heritage. Several land forts became visitor attractions, with one now an important national museum operated by the Royal Armouries. The fortunes of the sea forts also changed. All are now privately-owned, with the three most prominent restored as unique leisure and hospitality venues.
Royal Commission
Britain and France fought together in the Crimean War (1853-6). But tensions rose afterwards as France continued to build up its military strength. The French navy soon rivalled Britain’s own in terms of size and firepower, and France’s building of the revolutionary new steam-powered, ironclad battleship, Gloire, spread fears that a war was inevitable.
Only days before Gloire was launched, in November 1859, Britain’s prime minister, Lord Palmerston, appointed a Royal Commission to devise a suitable national defence strategy.
For Portsmouth, then the nation’s most important military base, there were two pressing concerns. The first was the implications of new weapons technology for Portsmouth’s existing defences, most of them Tudor or even earlier. They were built to resist attack from wooden ships powered by wind and sail. Steam-driven, armoured warships like Gloire, were an unpleasant new reality. Armed with new designs of breech-loading, rifled-barrel guns, the new “ironclads” would be able to pound the dockyard and naval base from well beyond the reach of Portsmouth’s current fortifications.
The second worry was that a French invasion force might not attempt a direct frontal assault on Portsmouth at all. Instead, it would land just along the coast, out of range of Portsmouth’s guns, to mount an attack from the mainland. If this were to happen, there was little to stop invaders reaching the City’s walls. Only Ports Creek, the narrow channel that divides Portsea Island from the mainland, would stand in their way.
“A Sure Base for Operations”
The Commission published its findings in February 1860, proposing new fortifications be concentrated around the most important military sites to maintain them as “sure bases for operations”. Portsmouth took centre stage. The recommendations put to Parliament in July 1860 called for additional fortifications all around the Harbour and Portsea Island, to address the weaknesses the Commission had identified.
Land forts would extend from Stokes Bay in the Solent around to Farlington at the northern edge of Langstone Harbour. On Portsea Island itself, existing chalk and earth embankments would be extended with a moat and bombproof casemates. Improvements would also be made to existing defences from Langstone Harbour entrance in the east to Gilkicker Point, on the Gosport side of Portsmouth Harbour’s entrance, in the west. To the south, the natural protection provided by the Solent’s many hidden sandbanks and shoals would be complemented by forts built on the seabed itself. These would guard the safe deep water channels into Portsmouth Harbour and through the eastern Solent towards Southampton.
The Solent forts were designed and built by military engineers under the overall direction of Colonel William Jervois of the Royal Engineers, who had been secretary of the 1859 Royal Commission. But factors beyond the military’s orbit soon intervened.
Dogged by political infighting and rival vested interests, as well as its sheer scale, complexity and cost, the programme to create “Fortress Portsmouth” quickly fell behind schedule. Revised deadlines, changed minds and escalating budget estimates led to fresh arguments and more delay. The local geography also played its part, with plans for a fort on Sturbridge Shoal in the Spithead anchorage then an alternative on Ryde Sand both being abandoned after the seabed in both locations was found to be too unstable.
In 1862, it seemed the project might be abandoned entirely, as fresh consideration was given to competing proposals for floating gun batteries or specialised turreted gunships. The impasse lasted two years before work restarted.
The Armstrong Gun
The challenges presented by building such massive constructions in the middle of a tidal seaway were not the only issue. Arguments also raged around the pros and cons of the new breech-loading, rifled-barrel guns.
Designed by Sir William Armstrong and formally adopted for land-based use in 1858, the new weapon had a clearly superior range and striking force to its smooth-bored, muzzle-loading equivalent. But the Admiralty, reliant for decades on tactics based around broadsides fired at short range, saw little benefit to be had at sea. The Navy’s highly-trained gun crews could closely match the early Armstrong gun’s performance and fire rate using conventional guns, they argued. Besides, their tests had shown that the more complex and costly Armstrong design lost accuracy and reliability as it heated up with repeated firing.
While France and the other continental navies quickly developed and improved on their own versions of Armstrong’s design, Britain formally abandoned breech-loaders in 1865. It would not be until 22 years later that the Navy would finally embrace the new technology with the launch in 1887 of HMS Collingwood.
In the meantime, Armstrong adapted his rifling system to suit their preferences, and the “RML” (“rifled muzzle-loader”) gun became the intended weapon of choice as the new Portsmouth fortifications rose up from their foundations.
Falling Behind
This only complicated matters for those building the sea forts. Specifications for the RML armaments to each sea fort kept changing. An 1871 decision to mount new 12-inch, 35-ton guns, for example, was changed in 1874 to a requirement for more powerful 12.5-inch, 38-ton guns. Not only were the new guns heavier, but their mountings were heavier, too. Their barrels were longer, and their recoil more powerful. Their shells weighed up to 90 kg more, requiring new storage and handling arrangements. But the more the construction of each fort advanced, the less space and scope there was to incorporate such necessary changes.
The result, with hindsight, was always going to be doomed to compromise. By the early 1880s, when the Solent forts were finally finished, not only had their original purpose long since gone but their relevance to Britain’s future defence needs had evaporated as well.
In the following years, some use was found for them. 1909, a row of concrete blocks was sunk out from the shores of Southsea and the Isle of Wight to block the eastern passage into Portsmouth Harbour and the Solent other than through the deep water channel between the two largest forts. During the First World War, the forts were partly re-armed with lighter but quicker-firing guns as a defence against fast torpedo boats, although no such attack ever came. In the Second World War, as the Portsmouth’s naval base and dockyard came under a sustained Luftwaffe bombing campaign, they were used as searchlight and anti-aircraft stations.
The formal disbandment of Britain’s coastal defences in 1956 led to their eventual disposal by the military.
The Solent Forts
There are four sea forts in total, although some documents refer to more. This reflects the changes that were made to the original scheme as work progressed, as well as historical inconsistencies in how they were named.
Spitbank
This is the fort nearest to Portsmouth Harbour’s entrance and so most familiar to residents and visitors. Built on the far side from Southsea Castle of the deep water channel which runs parallel with the Southsea shoreline, its function was to protect the Harbour entrance. Work on it began in July 1861 but was halted a year later and only restarted in 1867. The fort was completed in 1878.
With a diameter at its base of 162 ft (49 m) narrowing to 146 ft (44.5 m) at its upper level, and only a single gun floor, Spitbank is the smallest of the three forts in the Harbour approaches. Its circular stone and concrete foundations were laid directly onto the seabed at Spit Bank, which is the shallowest part of Spit Sand, the wider area of shallows outside the Harbour entrance after which the fort is named on maritime charts.
The water over Spit Sand is too shallow for larger vessels and the fort’s structure on this side reflects this with outer walls of brick vaulting faced with granite, designed to house six 7-inch RML (“rifled muzzle-loading”) guns.
The seaward side of the fort, facing out towards deeper water, was built to house and deal with much heavier weapons. The gun floor on this side is built in iron sections, with its outer face a “sandwich” of iron plate, wrought iron and teak 25 in (63.5 cm) thick. This side of the fort was designed for nine 10-inch RML guns. A further two guns were originally intended to be placed in turrets on the concrete roof but these were dropped from the final plans.
The lower level of the fort housed the shell and cartridge stores together with the kitchen and general store. Accommodation was provided for by two barrack rooms on the gun floor, each with space for 12 men, and quarters for two sergeants and one or two officers. Additional men, when needed, could sleep in hammocks. As with all the forts, the garrison had its own supply of fresh water from a central artesian well sunk in 1877 to a depth of 401 ft (122 m).
Although Spitbank never had need to fire its heavy guns, its armaments were upgraded several times. The 10-inch guns on the seaward side were replaced in the early 1890s with 12-inch, 35-ton guns while two 4.7-inch guns together with searchlights were built onto the roof in 1905 to counter attacks by smaller, faster craft. In the Second World War, two Lewis guns and a 40 mm Bofors gun allowed the fort to serve as part of the Harbour’s defences against a sustained Luftwaffe bombing campaign.
Spitbank remained military property until 1982 but is now owned and operated, following extensive restoration, by a hospitality and leisure operator.
Horse Sand
Horse Sand, like its No Mans Land “twin”, is a considerably bigger structure than Spitbank.
Built in a similar manner, with circular foundations laid directly onto the seabed, its diameter is 240 ft (73 m) at its base, narrowing to 204 ft (62 m) at its upper level. The basement level harboured 24 shell stores and 14 cartridge stores. Above this are two iron gun floors built around the fort’s circumference, one on top of the other. Both are separated by a courtyard from the fort’s inner core which housed officers’ quarters and offices. The gun floors are built in the same way as those of Spitbank, with a protective outer layer of armour formed from plate iron, wrought iron and teak sandwiched in layers.
Work on the fort began in July 1861 before being suspended from 1862 to 1865, when it restarted. On its completion in March 1880, Horse Sand’s gun floors were able to house a total of 49 guns with another 10 in roof turrets. By 1874, its specification had been changed to upgrade its heavy guns to the latest 12.5-inch, 38-ton guns on its lower gun floor and 10-inch, 18-ton guns on the gun floor above. The fort became a test-bed for further developments in artillery, including the use of new hydraulic systems. In 1887, the outer ring of magazines in the basement level was filled in to provide more substantial footings for new 12-inch 45-ton guns on special mountings.
In 1909, the fort became the southernmost extension of the concrete block submarine barrier laid to deny access to Portsmouth Harbour other than under Horse Sands’ and No Man’s Land’s guns. While some of the heavier guns were removed or replaced in following years, new quick-firing, breech-loading guns were added to counter the threat of attack by smaller craft.
During the Second World War a boom was laid across the open water between Horse Sand and No Mans Land forts to improve the security of Harbour approaches. Early electronic equipment was also installed to detect the approach of enemy craft.
Horse Sand Fort was released by the military in 1993 and has since been purchased by the same company that owns Spitbank and No Man’s Land forts. It has been restored and is intended to be run as a “living history” museum recapturing the atmosphere and circumstances of its part.
No Man’s Land
Like Horse Sand, work on No Man’s Land Fort was begun in 1861, suspended in 1862 and resumed in 1865. It was completed in March 1880.
The fort has an almost identical specification tos that of Horse Sand. Only minor differences to its armaments reflect its location on the Isle of Wight side of the Portsmouth Harbour and Solent deep water approaches. Submerged concrete blocks run from it to the Isle of Wight shoreline, completing the 1909 submarine barrier that forces approaching shipping to pass between the two biggest Solent forts.
The problems the builders had in addressing the arms race of the late 19th century are evidenced by reports that none of the larger 12.5 inch 38-ton guns installed on No Man’s Land could be fired with full charges. This was due to the lack of sufficient space in which to manage their recoil. Despite such limitations, the fort was used to test new ammunition transport and gun management systems using a combination of electrical and hydraulic power. It became the first fort in Britain to incorporate such systems and also the first to be illuminated throughout by electricity.
Like its Horse Sand twin, No Man’s Land remained in active use throughout both world wars until the disbanding of the coastal defence system in the mid-1950s. It was given scheduled ancient monument status in 1967. Released by the military 20 years later it has been restored and converted as a luxury hospitality and leisure venue.
St Helen’s
Often overlooked as a former “Palmerston Folly”, St Helen’s Fort is the most distant from Portsmouth, standing on a shallow spit of land extending eastwards from Bembridge Point on the Isle of Wight. The smallest of the forts, it was not included in the Royal Commission’s original recommendation but was started in 1867 after plans for defences to be built on Sturbridge Shoal in the Spithead anchorage, and later on Ryde Sand, were abandoned. Problems with subsidence meant the fort was never completed as intended and had only three heavy guns fitted. Used in the Second World War as a searchlight station, St Helen’s is now a private property.
Did You Know?
- Popular legend has it that troops posted to garrison the Solent forts in the two world wars were picked from those who couldn’t swim. This was allegedly to ensure they would not try to desert from a posting that would have been cold, lonely and — as it proved – routinely uneventful.
- St Helen’s Fort is connected to the Isle of Wight mainland by a narrow causeway which is briefly exposed during the lowest tides of the year, normally in August. It has become the focus for an annual charity walk that is deliberately not publicised so as to keep participant numbers manageable, but which raises growing sums each year.
- As with the causeway to St Helen’s Fort, the apparently sweeping expanse of the Solent’s eastern entrance is characterised by dangerous shoals and shallows that have trapped many unwary sailors over the years. The marked deep water channel into Portsmouth Harbour is currently being enlarged ready for the arrival of the Navy’s two new aircraft carriers, HMS Queen Elizabeth and HMS Prince of Wales.
- The concrete blocks laid between Southsea beach and Horse Sand Fort, and from the Isle of Wight shoreline to No Man’s Land Fort, are still in situ having later been deemed too expensive to remove. Some blocks nearest the shore are revealed during the lowest tides and safe passages have been cleared for smaller craft. But they remain a hazard that, although clearly marked on maritime charts, still catches out careless yacht and powerboat skippers from time to time.