Sandgate Castle

Until the last years of Henry VIII the Crown had left coastal defence largely to local lords and communities, taking only a modest part in building and maintaining fortifications, and the works that existed were very limited in scale. In 1533 Henry broke with Pope Paul III in order to annul his long-standing marriage to Catherine of Aragon and remarry. Catherine was the aunt of the Holy Roman Emperor Charles V, who took the annulment as a personal insult, and in 1538 France and the Empire declared an alliance against Henry, with the Pope encouraging the two countries to attack England. An invasion now appeared certain, and in 1539 the King issued the order known as a device, giving instructions for the defence of the realm in time of invasion and for the construction of forts along the English coastline.

Sandgate was intended to hold a vulnerable point along the Kent cliffs just west of Folkestone, where an enemy force could land and make its way easily further inland. Construction was supervised by the Moravian engineer Stefan von Haschenperg, with Thomas Cockys and Richard Keys acting as commissioners for the project. In the first stages of the work in 1539 a team of 237 men was employed, masons, quarrymen, limeburners and wood fellers preparing the site, the masons drawn from as far away as Somerset and Gloucestershire. By that summer over 500 were at work, including labourers, bricklayers, carpenters and sawyers, and after a pause through the winter months 630 were on the castle in the July that followed.

The foundations rested on the underlying shingle of the beach, and the walls were built of Kentish ragstone, most of it collected from outcrops on the local beaches, with Caen stone used in the detailing; 459 tons of that Caen stone was recycled from the priories of Christ Church and Horton, which Henry had recently dissolved. The whole project cost £5,584. At the centre stood a circular keep with three ovoid towers and bastions around it on the north-west, north-east and south sides and a gatehouse to the north, all enclosed by two curtain walls. There were four tiers of guns in the finished work, from ground level up to the roof of the keep, and 142 firing points for cannon and handguns, their design closely resembling those at nearby Walmer and Deal.

Sandgate was completed by the autumn of 1540, and Henry may have come to it while he was visiting Folkestone in May 1542. Elizabeth I visited the fortification in 1573 and also used it to imprison the courtier Thomas Keyes for a period, after he married Lady Mary Grey against the Queen's wishes. In 1593 the castle was reported to be equipped with seven artillery pieces, one culverin, two demi-culverins, three sakers and one minion, along with muskets, bows and arrows. In 1609 the garrison comprised a captain and his lieutenant, five soldiers, two porters and ten gunners.

The mortar used in the castle was particularly poor and had begun to decay seriously by 1616. A survey that year showed the place to be substantially dilapidated, put the proposed repairs at £260, and noted that a 100-foot gun platform for ten weapons had been built along the southern walls to replace the original southern battery. A report of 1623 echoed the same problems and recorded that the sea had caused a third of the southern wall to collapse, the necessary repairs, including strengthening the walls, being projected at £560. Four years later, amid fears of war with France and Spain, the castle's captain Richard Chalcroft reported the fortification "neither habitable or defensible against any assault, nor any way fit to command the roads". An inspection team observed that it was straightforward to climb over the ruined walls and rotten timbers, and that the artillery had in consequence been dismounted and placed along the beach instead. The castle was probably not repaired until after 1638.

Sandgate Castle was seized in 1642 by Parliamentary forces at the start of the first English Civil War between the supporters of King Charles I and Parliament, although its captain, Richard Hippesley, remained in post. That war ended in 1646, and after a few years of unsteady peace the Second Civil War broke out in 1648. The Parliamentary navy was based in Kent, protected by the other Henrician castles of Walmer, Deal and Sandown, but by May a Royalist insurrection was under way across the county and the fleet joined the rebellion; Sandgate and its sister castles were occupied by the Royalists. Parliament defeated the wider insurgency at the Battle of Maidstone at the start of June and then sent a force under Colonel Rich to deal with the Kentish castles. Sandgate was still held by the Royalists that August, when Rich sent troops to prevent its garrison intervening to disrupt his assault on Deal and Sandown, but it was recaptured soon after.

Hippesley continued as captain of Sandgate through the early years of the interregnum until he was replaced in 1653, complaining afterwards that he had been unfairly treated and that Parliament owed him money. During this period the garrison was increased to a governor, two corporals, twenty soldiers and three gunners. When Charles II was restored to the throne in 1660 Sandgate and the other Device forts initially remained at the heart of the south coast defences, but their design was by now antiquated; the garrison was cut back to its pre-war levels and then reduced further in 1682 to only ten men. The castle had fallen into poor condition, and £200 was assigned in 1663 for its repair, to be met partly from the proceeds of lands around Sandgate confiscated from former supporters of Parliament.

Sandgate was still in use during the Napoleonic Wars at the start of the 19th century, but was heavily rebuilt. Brigadier-General William Twiss surveyed the south coast in 1804 and proposed a series of 58 new defensive towers along it, as part of which Sandgate would be converted into a "secure sea battery". After some opposition, and many delays within the War Office, work finally began in 1805. It lowered the height of the castle considerably, destroying much of the fortification in the process: the upper storeys of the keep, the towers, the covered passageways and the gatehouse were all demolished, and the resulting rubble was used to backfill the outer ward, effectively turning the inner ward into a dry moat. An esplanade and wall-walk built around the remaining outer walls supported at least eight gun emplacements.

The circular keep was turned into a Martello tower, now only two storeys tall and reached on the first floor by an unusual sliding drawbridge, supported on rails and able to retract into the floor. The modified castle was completed by 1808 and held eight 24-pounder guns along the outer wall, one on the roof of the southern bastion and another on top of the keep, with room for a garrison of 40 men. In 1859 it was re-equipped with heavier artillery, a combination of 32-pounders and 68-pounders, and a new magazine was built, specially designed to keep the gunpowder dry. The exterior gun emplacements were redesigned on the 1806 foundations, and the two that survive, in the north-east and north-west bastions, date from that work.

Coastal erosion remained a problem. By the middle of the 19th century the tides had reached the southern edge of the castle, and an 1866 report stated that the walls had been undermined by the sea. Protective piles were driven around the castle, but it was badly affected by flooding in 1875 and 1878, which created serious fissures in the stonework. The high costs of maintaining the property, combined with its dwindling utility, encouraged the government to sell the site in 1888 to the South Eastern Railway company, which intended to turn it into a railway station. It was then sold on to private owners, who created a small museum in the castle and sometimes opened it to the public for an entry price of one penny.

Severe storms in 1927 and 1950 undermined large parts of the castle, and by the time a new seawall was built in the early 1950s the southern third had been entirely destroyed. In 1975 Peter and Barbara McGregor began to restore the ruins with the support of the Department of the Environment, Kent County Council and the British Army, and Edward Harris carried out archaeological investigations between 1975 and 1979, excavating part of the 1806 esplanade to reveal the lower 16th-century stonework of the north-east tower. The keep was turned into a private residence. Lord Geoffrey Boot and his wife acquired the castle in 2000, and it is used by Boot's company, AMT South Eastern Ltd.

Sandgate is protected under UK law as a grade I listed building, a designation it has carried since December 1949, and as a scheduled monument. The two 16th-century ledger books from the original construction, written by the project clerk Thomas Busshe, survive in the British Library; 350 pages long, they form what the historian Peter Harrington has described as the "most complete building account of any Tudor fortification".