HMS Dolphin: Ninety-Five Years as the Spiritual Home of the Submarine Service

An Ancient Fort Gets a New Job

Fort Blockhouse at Gosport has guarded the entrance to Portsmouth Harbour since a timber blockhouse was first authorised there under Henry VI in 1431, with the current bastioned fort largely dating from a rebuilding between 1708 and 1714, and from 1873 the Royal Engineers used it to run the School of Submarine Mining, training men to lay and control underwater harbour defences.

The Royal Navy took over the site around 1904, establishing it as a Submarine Boat Station housing five Holland-class boats by 1905, home to the very first submarines Britain ever operated, including Holland 1 herself, launched in October 1901 and now preserved at the museum on the same site after being raised from the seabed in 1982, decades after sinking under tow to the scrapyard.

The establishment took its name, HMS Dolphin, from an old wooden sloop moored there for extra accommodation from 1906, and the whole site achieved formal status as an independent command under that name in August 1912, a detail worth clarifying since a commonly repeated 1924 commissioning date does not hold up under scrutiny and appears to be a mix-up with an entirely unrelated depot ship of the same name that had no connection to Gosport at all.

Where Every Submariner Learned Their Trade

For roughly ninety-five years, from 1904 until 1999, HMS Dolphin served as the acknowledged spiritual home of the Royal Navy Submarine Service, housing the Submarine School throughout that entire span, save for a wartime interlude when bombing forced a temporary relocation to Blyth in Northumberland.

The Submarine Service received its Queen's Colour at Dolphin on 8 June 1959 and the Honorary Freedom of the Borough of Gosport two years later, formal recognition of just how closely the town and the base had become entwined, and the elite Perisher submarine command course, still one of the most demanding leadership courses in any navy in the world, ran out of Dolphin for generations before submarine operations eventually shifted north to Faslane.

The Tower That Trained a Service, and the Disasters That Built It

Dolphin's most visually distinctive feature for over half a century was the Submarine Escape Training Tank, a roughly ten-storey Grade II listed tower built between 1949 and 1953 and first used for training on 13 July 1954, its circular steel tank holding nine hundred thousand litres of water and rising thirty metres, with airlocks at nine and eighteen metres allowing submariners to practise both unassisted and pressurised escape ascents.

Its construction was driven directly by tragedy.

On 12 January 1950, HMS Truculent sank in the Thames Estuary after colliding with a Swedish tanker, and although sixty-seven men managed to escape using breathing apparatus, most died of drowning or exposure in the tide before help could reach them, a disaster that, alongside the earlier prewar loss of HMS Thetis, prompted a formal safety review and directly led to the tank's construction at Gosport.

A second tragedy followed on 16 April 1951, when HMS Affray was lost with all seventy-five men aboard after departing Dolphin for a training exercise, Britain's last submarine ever lost with all hands, her wreck not located until that June and the precise cause of her loss still officially disputed by historians to this day.

The tank itself trained submariners from around fifteen different nations at its peak, some 4,500 a year through the 1960s and 1970s, an estimated one hundred and fifty thousand uses across its sixty-six-year working life, before pressurised training ended in 2012 and the tower finally closed in January 2020, its role taken over by a new facility at Faslane.

A Quiet Departure

The last submarine permanently based at Dolphin left in either 1993 or 1994, sources differ slightly on the exact year, as the Royal Navy's whole submarine flotilla gradually consolidated at Faslane in Scotland.

HMS Dolphin formally closed as an active submarine base on 30 September 1998, and the Submarine School itself closed for good in December 1999, relocating to HMS Raleigh in Cornwall, with the site reverting to its older name, Fort Blockhouse, that same December, closing out nearly a century of continuous service to the Submarine Service.

A Museum Shaped Like a Submarine

The Royal Navy Submarine Museum has operated on the site since 1963, originally inside HMS Dolphin itself, with a new complex opening in 1981 built around the preserved submarine HMS Alliance, and a purpose-built exhibition building, deliberately shaped like a submarine hull and housing Holland 1, opening in 2001.

Fort Blockhouse itself, however, remains largely dormant today, still owned by the Ministry of Defence but listed for disposal since 2016 and formally for sale since 2017, with redevelopment plans repeatedly stalling over the considerable cost of maintaining Haslar's ageing sea wall and a shortage of financially credible buyers, leaving one of the Submarine Service's most historically significant sites in a curious, unresolved limbo even as the museum beside it keeps its story very much alive.