Fort Blockhouse

Not to be confused with West Blockhouse Fort.

Fort Blockhouse
Gosport, England
Fort Blockhouse (centre) and the marina
Fort Blockhouse
Type	Fort, later submarine base
Site information
Condition	Complete
Site history
Built	1431, various additions until 1960s
In use	1431–1539 (as blockhouse) 1539–1956 (as battery) 1905–1998 (as submarine base) 1996–2020 (as training site) 2002- present (as RAMC barracks)
Battles/wars	Siege of Portsmouth (1642)

Fort Blockhouse is a former military establishment in Gosport, Hampshire, England, and the final version of a complicated site. At its greatest extent in the 19th century, the structure was part of a set of fortifications which encircled much of Gosport. It is surrounded on three sides by water and provides the best view of the entrance to Portsmouth Harbour. It is unique in that it was built over five centuries from its original construction as a blockhouse in 1431 to the final addition of submarine base structures in the mid-1960s. Coastal fortification was abolished nationally in 1956, and the fort has not been used in a military capacity since 2021.

The MoD plans to dispose of the site in 2025.

History

Early fortifications (1431–1667)

Fort Blockhouse from the water.

Following the burning of Portsmouth during the Hundred Years' War, money was set aside in 1417 to provide protection for Portsmouth Harbour. A blockhouse was first built on the Gosport side of the harbour in 1431 after authorisation by Henry VI. A chain was strung from Blockhouse point to a similar tower in Portsmouth, which could be raised to prevent entry to the harbour by enemy ships.

The blockhouse was replaced in 1539 by an eight-gun battery under the orders of Henry VIII after his divorce from Catherine of Aragon. Blockhouse was supported by secondary fort to the south from 1545 to 1556, named Haselworth Castle, though this was abandoned only eleven years after construction. A plan to move the dockyard from Portsmouth to Gosport in 1627 never came to fruition, though storehouses for the new docks were built on the site. In 1642, during the English Civil War, the fort was used to bombard Portsmouth, which was at the time under Royalist control.

Modernised fort (1667–1877)

The fortification was extensively reworked in 1667 when Bernard de Gomme installed new defences at the order of Charles II. Two towers, named James Fort and Charles Fort, were completed by 1679, though the full plans involved additional earthworks that were never constructed.

An 18th-century view of Portsmouth from Fort Blockhouse

An inspection in the early 18th century found that the defences had fallen into poor condition. In 1708 the fortifications were completely rebuilt, with 21 guns facing the sea and significant earthworks. The 1708 works are the oldest still present on the site. The defences to the north were expanded in 1757, in order to enclose the Weevil brewery, which in the preceding fifty years had become an important supply of beer for the navy. The fortifications from de Gomme's era were still present at the west side of the fort, and were in poor condition by that time. The Weevil estate was purchased in 1761 and the land was redeveloped into the Royal Clarence victualing yard. New defences were constructed for Gosport in 1778, with the bastioned Fort Monckton situated on the ground that had been occupied by Haselworth Castle in the Tudor era.

Further renovations took place from 1797 to 1803, amid fears of French invasion. This created a line of bastions defending Gosport all the way from Blockhouse Point up to Forton Lake on the far side of the town, with French prisoners of war making up a part of the construction workforce.

South Casemates of 1845–48 (being the third reconfiguration of de Gomme's 21-gun battery).

Much of fort Blockhouse was remodelled in 1813, with further modifications to the battery taking place in 1825 and adjustments to the bastion in 1845. The defences outside of Blockhouse point were however not effectively maintained, with James Fort and Charles Fort falling into ruin in the early 19th century. The defences were considered obsolete by the 1859 Royal Commission on the Defence of the United Kingdom. The stone parapet was reworked in 1863, and additional guns were added at the rear of the site.

Mining and submarine base (1877–1998)

Modern buildings within and beyond the Fort, including the prominent Submarine Escape Training Tower.

The Fort Blockhouse Submarine Mining Establishment was founded in 1877, with additional structures added to the Blockhouse complex including a crane and pier, along with a light rail system to move explosives. Additional administrative buildings were added in 1884, when the site also became home to the School of Submarine Miners. The pier was extended in 1888, and additional rooms continued to be added for storage and tests until 1891. The Portsmouth Militia Division, which had recently been performing experiments with torpedoes that could be launched from a coastal defence at Fort Monkton, also moved to Blockhouse in 1892 and remained until 1907. The two forts were linked with a narrow gauge railway, which also extended to the facilities in Stokes Bay which were still in use for this purpose. The railway survived into the early 20th century.

Blockhouse was turned over to the Royal Navy in 1905 and, as HMS Dolphin, it became the home of the Royal Navy Submarine Service. The Napoleonic era defences that had extended out to loop around the west side of the town were removed, in order to facilitate transportation. Between the two world wars, the establishment expanded beyond the lines of the original fort on Blockhouse point however, and the prominent submarine escape tower was built in 1953, and opened in 1954. The need for such a training facility had been made apparent by the loss of HMS Truculent in 1950. The battery of the fort was disarmed in 1956, and additional buildings were added to support submarine operations in the mid-1960s. The end of the Cold War brought with it a reduction in defence requirements, with the threat of Soviet submarines having passed- and so in 1992 it was announced that the smaller submarine fleet would be leaving HMS Dolphin and moving west to HMNB Devonport. The last submarine left Dolphin in 1994. HMS Dolphin was declared surplus to requirements in 1996 and Dolphin was formally decommissioned in 1998.

33 Field hospital and Defence Medical Training facilities (1996–2018)

Aerial view of Fort Blockhouse from the north-west (2024).

The Defence Medical Training Organisation (DMTO) was established at Fort Blockhouse in 1996 (close by what was then the tri-service military hospital at Haslar). At the same time, part of the Blockhouse site became the Royal Defence Medical College (RDMC), which provided initial and advanced training for all military Medical Officers and nurses and the majority of medical technicians. Following the decommissioning of HMS Dolphin in 1998, RDMC became responsible for the whole Fort Blockhouse estate. In 2002, however, after Haslar's closure had been announced, the college relocated from Gosport to Birmingham (where the Royal Centre for Defence Medicine had been established the previous year); it now forms part of the University of Birmingham Medical School.

After the closure of the college, the Defence Medical Education and Training Agency (successor to the DMTO) remained, with its headquarters in the Mackenzie Building at Fort Blockhouse; the DMETA maintained a 'small residual training facility' on the site, which was connected with the local Ministry of Defence Hospital Unit. The DMETA was wound up in 2008, and its functions relocated to DMS Whittington as part of Joint Medical Command.

In 1996, 33 Field Hospital relocated to Fort Blockhouse following the closure of Cambridge Military Hospital, Aldershot, where it had been established in 1985. Over the next twenty years the hospital was regularly deployed, to Kosovo, Iraq and Afghanistan, the last deployment being to South Sudan in 2017. 33 Field Hospital was disbanded on 1 December 2018, after 33 years’ existence.

SETT training facility (1998-2020)

The SETT viewed from above (2004).

Although the submarine base was closed in 1998, the Royal Navy Submarine School (RNSMS) remained at the fort until 23 December 1999, and some training continued at Blockhouse for a further twenty years: the submarine school was relocated to HMS Raleigh in Cornwall, with pressurised training remaining at the Blockhouse facility until 2008. The Submarine Escape Training Tank (SETT) remained in service until it was finally closed in January 2020.

Future

Planned disposal

In 2016, it was announced that Fort Blockhouse would be disposed of by the Ministry of Defence in 2020, as part of a wider package of reductions in defence estate. Surveys were undertaken from January to March 2020 to determine which structures at the site would become listed buildings, and major job cuts took place at the end of the year. The disposal date was later extended to at least 2023, and once more to 2025.

External links

• Victorian Forts data sheet
• Fort Blockhouse and Submarine Mining on the Fort Gilkicker website