The fort was equipped with a variety of large-calibre artillery guns and the most modern defensive facilities of the time, including shell-proof casemates protected by granite facing and cast-iron shields.

Its lengthy construction and the rapid pace of artillery development at the time meant that it was practically obsolete for its original purpose within a few years of its completion.

East Tilbury, which stands at the western end of the section of the Thames known as Lower Hope Reach, was fortified long before the building of Coalhouse Fort due to its vulnerability to seaborne attackers.

The attack prompted the building of Cooling Castle on Kent's Hoo Peninsula between 1380 and 1385 but there was initially no corresponding move to improve the defences of East Tilbury.

[1] Appeals from the local people led to the Crown agreeing in July 1402 to build an earthen rampart and towers to protect the settlement.

[1] Henry VIII ordered the construction of an artillery blockhouse at East Tilbury in 1539–40 as part of a major scheme to fortify the coastline of England and Wales.

The French did not test the Thames defences, despite an invasion scare in 1804, and the battery was abandoned along with those at Lower Hope Point and Shornemead following Napoleon's final defeat in 1815.

As the American Civil War was soon to show, it was quite possible for the warships of the day to run past forts and attack up coastal rivers.

Construction began on this basis in July 1861 but as the work progressed the design was changed, leaving the fort with only a single tier of casemates.

[12] The rapid development of artillery weapons in the late 19th century meant that the casemate style of fortification had become virtually obsolete within a decade of the fort's completion.

This contained six much more powerful breech-loading (BL) guns on Moncrieff disappearing carriages within concealed emplacements facing east up the river.

Instead, part of the fort's front was covered with a sloping glacis made of earth, blocking the casemates and filling the inner defensive ditch.

The larger guns were intended to support those at East Tilbury Battery while the smaller ones provided a defence against fast-moving vessels such as destroyers and torpedo boats.

[18] Following the end of the war, it was proposed in 1924 that Coalhouse Fort should be re-equipped with 4-inch guns but post-war defence cuts meant that this plan was abandoned.

The continuing development of artillery firepower meant that the forts and batteries further downriver took on an increased responsibility for the forward defences of the Thames.

A detached concrete observation tower was built just north of the fort for use as an Extended Defence Officer's Post, to control the electrically detonated mines that had been laid in the river.

[21] They were supplemented by a detachment of Wrens who operated a degaussing range established at Coalhouse Fort in 1943 under the name of HMS St Clement.

[23] Outbound ships passed over submerged sensors which detected whether the steel in their hulls had been demagnetised to a sufficient extent to make them undetectable by German magnetic mines.

[21] As one of the Wrens later recalled, they found themselves "surrounded by a wonderful array of young men, soldiers and marines of all ranks – and we were the only girls in sight.

As HMS St Clement III, the fort's last military designation, it was used after 1946 by the Admiralty for training Sea Cadets and nautical youth groups.

The casemates are faced with massive slabs of granite and have iron gun ports to protect the gunners from splinters dislodged by incoming fire.

The magazine workers wore special clothes and shoes to eliminate the risk of striking sparks and the floors of the cartridge stores were covered by wooden battens.

The barracks provided accommodation for a wartime complement of six officers and 180 NCOs and men, though in peacetime only small maintenance detachments occupied the fort.

Although much of the barracks is now in poor condition, two of the kitchen ranges still survive and two rooms still contain service crests painted on their walls during the Second World War.

[26] The roof of the fort, accessed via steps up from the open battery, was altered substantially during the first half of the 20th century to accommodate new guns and other structures.

These include emplacements for 5.5-inch and 6-inch guns as well as 12-pdrs, searchlight positions, shelters, an observation post, a fire control building, a machine-gun parapet on the north caponier and a Royal Navy monitoring station.

This stands atop a brick building in which the power plant, electrical equipment radar screen and personnel accommodation were located.

Various items of 20th century military equipment were displayed in the interior of the fort; the casemates housed reconstructions and small military-related museums.

The British director Christopher Nolan had seen the TV series and decided that he wanted to set the film's opening scenes in the fort.

[37] English Heritage provided an emergency grant in 2009, supplemented by Thurrock Council and the filming fee from Warner Bros. for Batman Begins, to help make £200,000 worth of repairs to the gatehouse.