Skip to content

Site Visit – Slough Fort, Allhallows

Slough Fort (so named due to its proximity to Slough hamlet to the north west) was built between 1861 and 1867 to combat a ever growing threat from the French who were bolstering their coastal defences and naval fleets. One of many stone built forts built along the Kent coastline, the main role of Slough was to prevent the enemy fleet from entering either the River Thames or River Medway; two vitally important channels. The River Thames leading to the Capital, and the River Medway housing Chatham dockyard, the British pride of naval shipbuilding. The initial phase of construction built Slough as a single tower sitting proud on the high ground of The Brimp with seven covered emplacements giving 180 degrees of fire.

Despite being completed in 1867, the first 7-inch RBL (rifles breech loading) guns arrived 4 years later in 1871, but these weapons lacked punch and in 1891 the fort was upgraded to house 9.2-inch and 6-inch able to deter ships out to 10,500 yards. The new weapons enabled Slough to dominate the river approaches to London and were of a revolutionary design, and were housed in a newly designed Twydall profile fort with eastern and western wings. While the previous fort was intended to be a highly visible deterrent to enemy shipping, the new fort of 1891 was hidden behind earthen banks and housed new ‘disappearing guns.’ In conjunction with new smokeless propellants, this steam and hydraulic mechanism enabled the guns to remain hidden below the horizon until firing, when they would raise over the casemate to engage the enemy, fire, and the recoil of firing would facilitate the lowering of the guns and pressurising of the system in preparation for further firings.

Thankfully the fort never saw action against an invading enemy fleet, but continued to be manned during WW1 where the ground defences were strengthened, while the end of the war saw the fort finally disarmed as the capability to protect the Thames fell elsewhere. The last piece of military history in this fort came in WW2 when three anti-aircraft guns were installed on the roof of the old fort, the remains of which remain today.

I visited the fort on Saturday 29 July 2017 during an official open day organised by the Slough Fort Volunteers Group. The fort is still in the ownership of the holiday park, however it is hoped that soon the volunteer trust will take over the management of this monument and continue to uncover more of its history. A potted history from the publication by Victor Smith, August 2016.