Editing Fort Blockhouse (section)

===Royal Engineer Submarine Mining Establishment (1873–1907)===
In 1873 Fort Blockhouse began to be used by the [[Royal Engineers]] as a base for the deployment of remote-controlled [[submarine mines]] as a line of defence for the harbour.<ref name="Brown1910">{{cite book |last1=Brown |first1=William Baker |title=History of Submarine Mining in the British Army |date=1910 |publisher=Royal Engineers Institute |location=Chatham |page=130}}</ref> At the edge of the headland, to the north of the fort, they built a short pier and several buildings over time, including a set of boathouses and cable sheds (which are still ''in situ'' as of 2024, alongside an associated [[slipway]]).<ref name="2007PeninsulaCAA" /> The casemates of the north bastion were converted into stores for mine casings and other new buildings were erected around the site, along with a light rail system to move the mines and explosives.<ref name="nhle1" /> 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.<ref>{{cite web|url=https://www.gosportheritage.co.uk/fort-blockhouse-our-most-popular-historical-visit/|title=Fort Blockhouse|date=11 August 2022 |publisher=Gosport Open Days|access-date=23 August 2024}}</ref>

As a fort, Blockhouse was increasingly seen as obsolete and its armament was accordingly reduced, from ten [[RML 64-pounder 58 cwt|RML 64-pounder]] guns in 1885 to three in 1888 (three machine guns were also provided, to protect the associated naval minefield). Subsequently five [[QF 12-pounder 12 cwt naval gun|12-pounder quick-firing guns]] were installed to combat the emerging threat posed by fast [[torpedo boats]].<ref name="nhle1" /> In 1893-94 a [[defensive boom]] was provided, which could be deployed to seal off the harbour entrance (analogous to the old chain defence).<ref name="2007PeninsulaCAA" /> 

In 1892 a new School of Submarine Mining was established on a site at [[Stokes Bay]] (close by [[Fort Gilkicker]]), which had previously been used for testing and experimental work. That same year the Royal Engineer companies moved from Fort Blockhouse to Fort Monckton; in their place a linked [[Militia (United Kingdom)|militia]] unit (the Portsmouth Militia Division (Submarine Miners) Royal Engineers), previously based at Fort Monckton, moved to Fort Blockhouse where they remained until 1907.<ref name="Brown1910" /> The two forts were linked with a narrow gauge railway, which also extended to the facilities in Stokes Bay; the railway survived into the early 20th century.<ref>{{Cite web|url=https://www.fortgilkicker.co.uk/mining.htm|title=Fort Gilkicker: Stokes Bay: Fort Monckton and the Submarine Mining Establishment|website=www.fortgilkicker.co.uk}}</ref>