Fort Amherst is a Napoleonic-era military fortress in Chatham, Kent, England. It was constructed between April and October 1756 at the southern end of the Brompton Lines during the Seven Years’ War, with the primary purpose of defending Chatham Dockyard and the River Medway from a potential French invasion. The fortifications were later significantly expanded during the Napoleonic Wars. Today, Fort Amherst is open year-round as a visitor attraction, offering guided tours through its extensive tunnel complex.
History
thumb|right|The defences in 1770.
The primary purpose of all the Medway fortifications was the defence of the Naval Dockyard. This was largely the result of the Raid on the Medway 12 June to 14 June 1667 when the Nederlandse Staatsevloot (Dutch State Fleet) inflicted heavy damages on Chatham Dockyard. Defences were planned for Chatham Dockyard from 1708 and land was then acquired by two Acts of Parliament. These were the Fortifications Act 1708 and the Fortifications Act 1709. The land was surveyed in April 1715 by Duke of Marlborough. The first plan of defences was an enceinte (ring of fortifications), from Gun Wharf, Chatham, to north of the village of Brompton.
From January 1755 to August 1755, the 'Prince of Wales' Bastion, 'Prince Williams Bastion', 'Kings Bastion', 'Prince Edwards Bastion', 'Prince Henry's Bastion' and the 'Prince Fredericks Bastion' were all built. The fortifications were designed in January 1755 by Captain John Peter Desmaretze of the Board of Ordnance and consisted of a earthwork ditch and a parapet.
In June 1757, an infantry barracks (for a troop garrison) was built to man the defences. Amherst Redoubt later became Fort Amherst. Each was equipped with 14 42-pounders, 10 9-pounders, 8 6-pounders and 2 4-pounder guns.
In February 1779, during the construction, workmen found an existing foundation of a Roman building. Several finds, including pieces of Roman brick and tile, were made. Roman coins were also found, including one of the Empress Faustina, and one of the Emperor Claudius. The finds were recorded by Rev. James Douglas, working as Lt Douglas with the Royal Engineers 'North Lincs Militia, who later wrote a book describing all of his archaeological research - Nenia Britannica.
thumb|right|The defences in 1812.
During the Napoleonic Wars (1803–1815) the Chatham defences were enlarged and considerably strengthened. Further batteries were added (such as the Cornwallis Battery) and the ditches revetted (lined with brick), His plan for the Chatham Lines, drawn by Joseph Heath and dated January 1755, is kept at the British Museum.
Also, from September 1802 until June 1811, prisoners, mostly convicts from St Mary's Island,
Fort Amherst has been described by English Heritage as the most complete Napoleonic fortification in Britain and as such has great national historical significance.
Fort Amherst was still in use during the Second World War when it served as an Air Raid Warning Command Post for the Air Raid Precautions (ARP) and the Royal Observer Corps (ROC). Halloween Tours have also taken place, where guests make their way through the dark rooms and passages.
On Sundays, during the summer 2008 season, Fort Amherst was open to the public, without charge, to promote the Great Lines Heritage Park and the proposed World Heritage Site application for Chatham Dockyard and its Naval Defences.
In 2012 the 200th anniversary of the establishment, under Royal Warrant of the Royal Engineers at Brompton Barracks (the Royal School of Military Engineering), was marked by a team of Royal Engineers designing, building and assembling the Bicentenary Bridge which leads to a part of Fort Amherst also known as Spur Battery and to the Inner Lines, that were the Napoleonic Defensive Ditches. These parts of Fort Amherst are accessible only at special times and during guided visits.
During 2012 Fort Amherst received about 20,000 visitors.