Fort Blockhouse
Fort Blockhouse is one of England's most historically significant coastal fortifications, occupying a commanding position at the tip of the Gosport Peninsula at the entrance to Portsmouth Harbour. This ancient defensive structure has stood guard over one of Britain's most strategically vital stretches of water for more than five centuries, controlling access to the naval anchorage at Portsmouth from the western shore. Today it serves as the home of HMS Dolphin, the Royal Navy's submarine training establishment, which means the site is a working military installation and not generally open to the public. Its combination of medieval origins, Tudor expansion, Victorian engineering, and twentieth-century submarine heritage makes it one of the most layered and fascinating military sites in Britain.
The origins of Fort Blockhouse trace back to the late fifteenth century, when a timber blockhouse was first constructed on this narrow promontory to provide artillery cover across the harbour mouth in conjunction with the Round Tower on the Portsmouth side. Henry VII ordered improvements to these defences around 1495, recognising that Portsmouth Harbour was the gateway to England's most important naval base. The name "Blockhouse" derives directly from this original structure, a term used at the time for a simple defensive artillery emplacement. Over the following centuries the site was repeatedly upgraded and expanded as both the technology of warfare and the importance of Portsmouth as a naval centre grew. Tudor and Stuart fortifications gave way to more substantial Georgian and Victorian works, with the latter period seeing the construction of substantial brick and earth ramparts capable of mounting heavy guns to counter the threat from ironclad warships.
The Victorian transformation of the site was extensive and reflects the anxious refortification of British coastal defences following the Royal Commission report of 1859, which identified serious vulnerabilities in England's naval harbours. The fort was substantially rebuilt and enlarged during this era, with the earthwork banks, ditches, and brick-lined gun emplacements that still define much of its physical form today. The sheer scale of the Victorian earthworks, with their carefully graded slopes and deep protective ditches, give the site a brooding, purposeful quality even from a distance. The brickwork of the internal buildings, many of which survive from the nineteenth century, has the characteristic solidity of Victorian military construction, built to absorb bombardment and last for generations.
In the twentieth century, Fort Blockhouse took on an entirely new identity as the centre of Britain's submarine service. HMS Dolphin was commissioned here and became the Royal Navy's primary submarine base and training establishment, home to generations of submariners who trained, lived, and departed for patrols from this peninsula. The site holds a special place in the history of British naval warfare, particularly during the two World Wars when submarines based here played a critical role in both the Atlantic and Mediterranean theatres. The submarine escape training tower, a tall cylindrical structure that once dominated the skyline and was used to train crews in emergency escape procedures, became one of the most recognisable features of the Gosport waterfront.
Standing near Fort Blockhouse, even from the accessible waterfront areas, one is immediately struck by the intensity of the marine environment. The entrance to Portsmouth Harbour is extraordinarily busy by the standards of British coastal waters, with ferries crossing to the Isle of Wight, naval vessels of various sizes, and commercial shipping all moving through the relatively narrow channel in close proximity. The tidal currents here are strong and the water is frequently choppy, giving the spot a sense of raw, working energy that is quite different from quieter stretches of the English coast. The smell of salt and diesel mingles in the air, and the sound of gulls, ship horns, and the rumble of ferry engines provides a constant maritime soundtrack.
The surrounding area of Gosport is itself a place of deep naval character. The waterfront along the harbour has been substantially opened up in recent decades, with a pedestrian path providing views across to the historic dockyard at Portsmouth, where the masts of HMS Victory can be seen rising above the rooftops. The Haslar peninsula, immediately adjacent to Fort Blockhouse, was home for many years to the Royal Hospital Haslar, a magnificent Georgian naval hospital that is now being converted for residential use. The nearby Explosion Museum of Naval Firepower at Priddy's Hard offers an accessible and informative look at the naval heritage of the area, and the Gosport Ferry provides a short, atmospheric crossing to Portsmouth itself, allowing visitors to approach the fort from the water and appreciate the strategic logic of its position.
Access to the interior of Fort Blockhouse remains restricted given its ongoing status as a military facility, though the Royal Navy has made efforts in recent years to open aspects of the submarine heritage to public engagement. The Submarine Museum at nearby Gosport, which houses HMS Alliance and provides a comprehensive account of British submarine history, is the best public destination for those interested in the history associated with this site. The museum is just a short distance along the waterfront and offers the opportunity to walk through a real submarine and understand the world of the submariners who trained at Fort Blockhouse. Visiting Gosport on a weekday offers the best combination of activity and accessibility, and the entire waterfront area can be explored on foot in a half-day, ideally combined with a trip across the harbour to Portsmouth Historic Dockyard.