Arrogant Block, Fort Blockhouse


Heritage Category:
Listed Building
List Entry Number:
Date first listed:
Statutory Address:
Fort Blockhouse, Haslar Road, Gosport, PO12 2AB


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Statutory Address:
Fort Blockhouse, Haslar Road, Gosport, PO12 2AB

The building or site itself may lie within the boundary of more than one authority.

Gosport (District Authority)
Non Civil Parish
National Grid Reference:


A defensible barrack block. Built in 1845 to 1847 but altered and extended in the early and late C20. 

Reasons for Designation

Arrogant Block, built as defensible accommodation in 1845 to 1847 at the artillery fort known as Fort Blockhouse and altered and extended in the early and late C20, is listed at Grade II for the following principal reasons:

Architectural interest:

* as bombproof groin-vaulted casemates and other ranks accommodation built in 1845 to 1847 to form part of the defensive enceinte of a key bastioned artillery fort that defended Portsmouth Harbour;

* as other ranks accommodation constructed at a time when permanent barracks were relatively rare;

* for the sympathetic early-C20 alteration and extension to accommodate the burgeoning accommodation demands of the Submarine Service.

Historic interest:

* as casemates and other ranks accommodation built in 1845 to 1847 and incorporated into the enceinte of a bastioned artillery fort that was central to the defence of Portsmouth Harbour, subsequently becoming a Royal Engineers establishment for the use of fixed minefields for harbour defence in the late C19, before serving as a principal base and spiritual home of Britain’s submarine service during the C20.

Group value:

* with the scheduled artillery fort of Fort Blockhouse, and the contemporary north-west officers quarters known as Thames Block, the former guardhouse, the former gatehouse datestone and the cannon bollard, along with buildings from other phases of the Fort's development; the Admiralty boundary stone (C18), Submarine Memorial Chapel (1917), the submariners’ memorial (late-C20) and the Submarine Escape Training Tower (late-C20), all of which are listed at Grade II.


Fort Blockhouse is sited on the western side of the entrance to Portsmouth Harbour at the end of a peninsula joined to Haslar by a narrow neck of land. A timber blockhouse was recorded on the site in the early C15. It stood opposite The Round Tower (NHLE 1386901) on the eastern side of the harbour entrance; a chain between the two securing the entrance against enemy ships. In about 1538 the west side was refortified with the addition of Lymden’s Bulwark but by the late C16 the fortifications were derelict. In the late C17, during the Second Dutch War (1672-1678), concerns over the vulnerability of naval dockyards to attack led to new schemes by the great fortress engineer Sir Bernard de Gomme to strengthen Portsmouth’s defences. An L-shaped battery was built on the site. A plan of 1668 shows a fort with defences facing the land and sea. In about 1709, there was major reconstruction work. The fort’s south-west defences were considerably strengthened with a redan, moat and outer work, as well as a south-east sea battery. The remaining north-west and north-east sides of the fort were enclosed by oak palisades with an angled bastion to the north. In the early C19 further work was undertaken, including the northwards extension of the western face of the west demi-bastion and extensive remodelling of the sea battery. Between 1845 and 1848, the sea battery was further strengthened and new casemates were built on the north and the eastern sides of the fort, as well as a limestone-faced north bastion. However, the advent of larger rifled cannon meant the defences became increasingly obsolescent as the C19 wore on.

In 1873 Fort Blockhouse was taken over by the Royal Engineers who were engaged in the use of fixed minefields as a means of harbour defence. A loading shed, workshops, mess room, boat and cable sheds, and a jetty were built. In 1904, the fort became a submarine base with the addition of new jetties and submariners accommodation. The hulk HMS Dolphin was also brought to the site to provide further accommodation and in 1912 gave its name to the newly established independent command. During the First World War, the base was the Royal Navy’s principal submarine depot and a memorial chapel was erected in 1917. A mock submarine control room known as an ‘Attack Teacher', was also erected along the northern curtain wall; only traces in the brickwork now remain. After the war, the outer C18 defence works were reduced, the moat partly infilled, and several buildings constructed within the fort interior, outside the main gate and surrounding it. In 1935 to 1937, a new headquarters was built for Rear Admiral, Submarines (commander of the service) with an operations room and communications facilities. At the outbreak of the Second World War, HMS Dolphin was home to 5th Submarine Flotilla. Operations were conducted in the Channel and the Bay of Biscay, and in June 1944 X-craft from HMS Dolphin were used to mark the D-Day landing beaches. After the conflict HMS Dolphin resumed its role as the main base for the submarine service, rising in prominence in the mid-1960s when the service provided the country’s nuclear deterrent. The base expanded with many new buildings on the land to the south-west of the peninsula. However, the end of the Cold War in 1991 led to a major reappraisal of defence requirements, and HMS Dolphin closed in 1998. The Submarine School was transferred to HMS Raleigh at Torpoint, Cornwall, and the Defence Medical College was established at Fort Blockhouse; the base being occupied by 33 Field Hospital. In 2016 the government confirmed that Fort Blockhouse was to close; the estimated date for disposal is 2022.   Arrogant Block was originally built in 1845 to 1847 as bomb-proof barrack accommodation. It was formed by a number of interconnected casemates with access on to the top of the fort wall to the north and south. Loop-holed parapets were provided along the eastern wall and the north elevation had low, narrow, horizontal embrasures and an upper, loop-holed parapet, both probably for musketry. On the western courtyard side of the barracks, iron pintles set into stone blocks at the sides of the window openings suggest that they were protected with armoured shutters. The original plan would probably have comprised a single, high-ceilinged, open barrack room with latrines and kitchen to the southern end.   A map of 1905 shows seven sets of steps to the west elevation, suggesting seven entrances. Steps up to the fort wall at the northern and southern ends are also evident and the southern end of the building is annotated as a latrine and a cookhouse.

By the outbreak of the First World War, Fort Blockhouse was home to the Royal Navy Submarine Service and seamen and stokers were housed in Arrogant Block. During the 1920s the quantity and standard of accommodation at Blockhouse was considered to be an issue and a statement read out in Parliament in March 1929 noted that further work was underway (Hansard 1929). Around 1928, Arrogant Block was extended by a further storey, under a light, steel-framed roof. Further windows were added to the elevations and mostly set within the curve of the casemates; the central examples marking the positions of the former entrances. Even though Thames Block was also extended around the same time, accommodation across Fort Blockhouse continued to be an issue with Hansard (1931) recording that ‘men are sleeping on the floors and tables and the petty officers are in the old instruction shed’.

In the later C20 a two-storey, flat-roofed ablutions extension was added to the southern end of the block and a stair tower to the eastern side to improve access to the first floor. The entrances to the western side were further reduced and a single new entrance created. The accommodation rooms are now laid out off spine corridors which run north to south and the fixtures and fittings are all late C20 and functional.


A defensible barrack block. Built in 1845 to 1847 but altered and extended in the early and late C20.    MATERIALS: red stock brick and vitrified brick in Flemish bond (original building) or stretcher bond (extensions) with stone detailing, replacement uPVC windows and a slate roof.   PLAN: a two-storey building with a storage attic, which is rectangular in plan. The main entrance is towards the centre of the principal west-facing elevation. It opens into a lobby which serves a spine corridor running north to south, off which there are multiple accommodation rooms. The stairs stand behind the lobby and the first floor has a similar layout with a door at the north end providing access to the top of the fort wall. A two-storey ablutions block (later C20 extension) is located towards the southern end of the building, which has a first-floor door in the south-east corner, which also meets the fort wall.     EXTERIOR: the principal elevation has 19 bays to the ground floor; three bays of openings to each of the five casemates flanked by two further end bays and a later two-bay ablutions extension at the south end. Each casemate has three, three-over-four pane sashes, apart from the fourth bay where the centre window is replaced by the main entrance. This has a pair of later C20, glazed, metal doors with a transom light, which are inset under a shallow, cantilevered stone porch. The window openings have flat, red brick arches and stone cills. Those to each side have two stone blocks inset into the brick work on each side, some of which carry metal pintles. The rubbed-brick headers to the central examples are later additions, as is the window opening and the brickwork above. The end bays have a single sash window beneath a replacement rubbed-brick header. The southern example also has a higher-set, narrow, brick header which corresponds to the earlier entrance opening. In front of the current entrance there is a pair of short concrete steps with tubular steel railings. A later, two-storey ablutions block is attached to the southern end of the building, which has a lower flat roof and casement windows, with stone lintels, stone storey band and brick cills. The C20 first floor of the main block stands above the casemates and is separated by a concrete storey band. It has regular sash windows of four-over-four configuration. These are inset between brick pilasters which have a plain, reconstituted stone band. The windows have concrete or stone lintels and cills.   The rear elevation faces east and is 18 bays long including a projecting stairwell near the centre and the two bays of the ablutions extension to the southern end. The arches of the casemates for the most part contain three, three-over-four pane sash windows which have concrete or stone lintels and cills. The central sashes are surmounted by a further multi-paned window of three-over-two panes. There are 13 bays to the first floor; largely formed of three-over-four pane sash windows. The projecting stairwell is lit by one large fixed window. The ablutions extension has uPVC casement and top-hung windows with stone lintels and cills.

The north elevation has three bays to the ground floor; a flush timber door with a shallow cantilevered stone porch flanked by three-over-four pane sash windows. There are five bays to the first floor comprising, from left to right: a flush timber door opening on to the parapet walk of the fort curtain wall; a uPVC casement window; and then three uPVC windows with fixed and top-hung lights.

The south elevation of the ablutions extension has five bays of windows to the ground floor; five uPVC casements beneath five uPVC clerestory windows. There are seven bays of uPVC casement windows to the first floor and a partially-glazed door opening on to the parapet walk of the fort curtain wall. Rising above the ablutions extension is the gable end of the main range, which has a tripartite window to the attic with a stone lintel and cill.   INTERIOR: the lobby has timber double doors* with glazed panels*. The groin-vaults of the casemates have been plastered but are partially visible in the ground-floor accommodation rooms. The corridors and the ground and first-floor accommodation rooms are functional in design with late C20 flush timber doors*, sink units*, shelves*, desks* and wardrobe units*. A dog-leg staircase with a steel balustrade leads up to the bedrooms on the first floor. The ablutions block fixtures and fittings* are late-C20 and functional.

* Pursuant to s1 (5A) of the Planning (Listed Buildings and Conservation Areas) Act 1990 (‘the Act’) it is declared that these aforementioned features are not of special architectural or historic interest.


Books and journals
Evans, D, Arming the Fleet: The Development of the Royal Ordnance Yards, (1770-1945)
Hall, K, HMS Dolphin: Gosport's Submarine Base, (2001)
Saunders, A D, Fortifications of Portsmouth and the Solent, (1998)
Williams, G H , 'The Western Defences of Portsmouth Harbour 1400-1850' in The Portsmouth Papers , , Vol. 30, (1979), Unkown
Francis, P, and Crisp, G, Military Command and Control Organisation, report for English Heritage (2008)
Historic England, Screening for Potential Listing Report: Fort Blockhouse, Gosport, Hampshire (2020)


This building is listed under the Planning (Listed Buildings and Conservation Areas) Act 1990 as amended for its special architectural or historic interest.

End of official listing

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