Sandgate Castle Sandgate Castle is a coastal castle at Sandgate near Folkestone in Kent . It was originally built as an artillery castle in 1539 – 1540 by Henry VIII of England as part of his chain of coastal defences in response to the threat of invasion . As these forts were devised by Henry VIII , they are known as Device Forts . It was built to defend a vulnerable stretch of coastline and due to its proximity to the French coast the site has been constantly defended and refortified . Construction 1539 – 1540 . The original castle , started in 1539 , is one of the most comprehensively documented of its time and the record still exists in the British Library . The total cost of the build was some £5 , 584 . 7s . 2d . The construction took 18 months and the accounts were closed on 2 October 1540 . The comptroller for the build period , Thomas Cocks , was paid the grand sum of £50 and the build employed around 500 people using 147 , 000 bricks , 44 , 000 tiles at 4s per thousand , a thousand cartloads of oak , 9 . 5 tons of lead and 4 . 5 tons of iron . 16d per day was paid for carts to haul stone and materials . Richard Lynsted was master mason . Sandgate ' s construction was supervised by Stefan von Haschenperg , who signed the accounts , though he was not often present . Haschenperg disagreed with other officials over the roofing materials . He preferred tar and pitch rather than less flammable lead , and this was a feature of his other building at Camber Castle . The original castle comprised a large , three - storey central keep surrounded by two concentric curtain walls . The inner curtain wall had three smaller , round towers and the outer curtain wall had a three - storey gatehouse to the north ( still in almost its original form ) and a rectangular building or barbican connecting it to the central keep . All of the buildings were originally roofed and the castle was designed so that it rose progressively from the outside in to provide up to four tiers of heavy guns . These were positioned behind 65 embrasures or gun ports and there were also gun loops in the lower levels of the towers and buildings to provide flanking fire . Sandgate ’ s sister castles were Sandown Castle , Kent , Walmer Castle and Camber Castle , in Kent and Sussex respectively . Sandown no longer exists , it was taken by the sea some years ago and Camber Castle is derelict . Walmer Castle , however , remains in the ownership of English Heritage and is the home of the Warden of the Cinque Ports . Subsequent history . During the castle ’ s long history Henry VIII visited in 1542 , Elizabeth I in 1572 and 1588 and Queen Victoria and Prince Albert in the late 1800s . In 1715 – 1716 the keep was re - roofed and the seaward battery rebuilt following damage by the spring tides . In 1805 – 1806 , during the Napoleonic wars , a major series of alterations were carried out on the castle to convert it into a gun fort / castle . The tops of the original defensive towers were removed and the central tower converted into a Martello - style tower mounting a coastal battery . In the late 1850s a new magazine was built and alterations made to the existing gun emplacements . Pillboxes were constructed at the castle during the 2nd World War . Bizarrely by today ’ s heritage standards , the castle was sold by the government due to defence cutbacks in 1889 . From the late 1890s the castle has gone through a number of nonmilitary reincarnations and uses . It became a private house in the late 1890s , but was again requisitioned for defence in both the 1st and 2nd World Wars . The South Eastern Railway Company applied to have the castle demolished in 1911 to provide a rail link along the coastline from Hythe to Folkestone In 1960 another application for demolition and replacement with a block of flats was rejected by the planning authority . The great storm of 1950 took around a third of the front portion of the castle , and most of the outer wall on the south side was destroyed by coastal erosion . New sea defences were built shortly thereafter to protect it for the future . Consequently the castle title deeds still contain ownership below the low water mark where the castle originally stood . For a period it became a museum , then a banqueting facility / restaurant and was finally converted into a permanent private dwelling in the late 1990s under the strict supervision of the Department of Environment and English Heritage . By then , the castle ’ s appearance had changed radically , with most of it re - faced during Napoleonic times , although there is evidence in the curtain walling of the original Tudor stonework , including French stone from Caen brought from the local monasteries of St Radegund near Dover and Christchurch , Canterbury , demolished during the dissolution . The castle is now in good heart as a private dwelling , and the main keep is topped with a distinctive stainless steel cap .