Dover Castle Dover Castle is a medieval castle in the town of the same name in the English county of Kent . It was founded in the 12th century and has been described as the " Key to England " due to its defensive significance throughout history . It is the largest castle in England . History . The site may have been fortified with earthworks in the Iron Age or earlier , before the Romans invaded in AD43 . This is suggested on the basis of the unusual pattern of the earthworks which does not seem to be a perfect fit for the medieval castle , excavations have provided evidence of Iron Age occupation within the locality of the castle , but it is not certain whether this is associated with the hillfort . There have also been excavations on the mound which the church and Roman Pharos are situated on and has been discovered to be a Bronze Age mound . The site also contained one of Dover ' s two Roman lighthouses ( or Pharoses ) , one of which still survives , whilst the remains of the other are located on the opposing Western Heights , across the town of Dover . On the site is a classic " montrol " ( campsite ) where the Normans landed after their victorious conquest . Saxon and early Norman . After the Battle of Hastings in October 1066 , William the Conqueror and his forces marched to Westminster Abbey for his coronation . They took a roundabout route via Romney , Dover , Canterbury , Surrey and Berkshire . From the Cinque Ports foundation in 1050 , Dover has always been a chief member — it may also have been this that first attracted William ' s attention , and got Kent the motto of Invicta . In the words of William of Poitiers : This may have been repairs and improvements to an existing Saxon fort or burgh , centred on the Saxon church of St Mary de Castro , although archaeological evidence suggests that it was actually a new motte and bailey design castle built from scratch nearby . Henry II to early modern times . It was during the reign of Henry II that the castle began to take recognisable shape . The inner and outer baileys and the great keep belong to this time . Maurice the Engineer was responsible for building the keep , one of the last rectangular keeps ever built . In 1216 , a group of rebel barons invited Louis VIII of France to come and take the English crown . He had some success breaching the walls but was unable ultimately to take the castle ( see The First Barons ' War ) . The vulnerable north gate that had been breached in the siege was converted into an underground forward - defence complex ( including St John ' s Tower ) , and new gates built into the outer curtain wall on the western ( Fitzwilliam ' s Gate ) and eastern ( Constable ' s Gate ) sides . During the siege , the English defenders tunnelled outwards and attacked the French , thus creating the only counter tunnel in the world . This can still be seen in the medieval works . By the Tudor age , the defences themselves had been superseded by gunpowder . They were improved by Henry VIII , who made a personal visit , and added to it with the Moat Bulwark . During the English Civil War it was held for the king but then taken by a Parliamentarian trick without a shot being fired ( hence it avoided being ravaged and survives far better than most castles ) in 1642 . Napoleonic . Massive rebuilding took place at the end of the 18th century during the Napoleonic Wars . William Twiss , the Commanding Engineer of the Southern District , as part of his brief to improve the town ' s defences , completed the remodelling of the outer defences of Dover Castle adding the huge Horseshoe , Hudson ' s , East Arrow and East Demi - Bastions to provide extra gun positions on the eastern side , and constructing the Constable ' s Bastion for additional protection on the west . Twiss further strengthened the Spur at the northern end of the castle , adding a redan , or raised gun platform . By taking the roof off the keep and replacing it with massive brick vaults he was able to mount heavy artillery on the top . Twiss also constructed Canon ' s Gateway to link the defences of the castle with those of the town . With Dover becoming a garrison town , there was a need for barracks and storerooms for the additional troops and their equipment . The solution adopted by Twiss and the Royal Engineers was to create a complex of barracks tunnels about 15 metres below the cliff top and the first troops were accommodated in 1803 . At the height of the Napoleonic Wars , the tunnels housed more than 2 , 000 men and to date are the only underground barracks ever built in Britain . At the end of the Napoleonic Wars , the tunnels were partly converted and used by the Coast Blockade Service to combat smuggling . This was a short - term endeavour though , and in 1827 the headquarters were moved closer to shore . The tunnels then remained abandoned for more than a century . The secret wartime tunnels . The outbreak of the Second World War in 1939 saw the tunnels converted first into an air - raid shelter and then later into a military command centre and underground hospital . In May 1940 , Admiral Sir Bertram Ramsey directed the evacuation of French and British soldiers from Dunkirk , code - named Operation Dynamo , from his headquarters in the cliff tunnels . A military telephone exchange was installed in 1941 and served the underground headquarters . The switchboard s were constantly in use and had to have a new tunnel created alongside it to house the batteries and chargers necessary to keep them functioning . The navy used the exchange to enable direct communication with vessels , as well as using it to direct air - sea rescue craft to pick up pilots shot down in the Straits of Dover . The Annexe level of the tunnel , excavated in 1941 was used as a dressing station ; it contained two operating theatres and had basic accommodation for patients . Later the tunnels were to be used as a shelter for the Regional Seats of Government in the event of a nuclear attack . This plan was abandoned for various reasons , including the realisation that the chalk of the cliffs would not provide significant protection from radiation , and because of the inconvenient form of the tunnels and their generally poor condition . Tunnel levels are denoted as A - Annexe , B - Bastion , C - Casemate , D - DUMPY and E - Esplanade . Annexe and Casemate levels are open to the public , Bastion is ' lost ' but investigations continue to gain access , DUMPY ( converted from Second World War use to serve as a Regional Seat of Government in event of an atomic war ) is closed , as is Esplanade ( last used as an air raid shelter in the Second World War ) . The Annexe level was excavated in 1941 to serve as a medical dressing station for wounded soldiers . Soldiers would be sent for emergency treatment in the tunnels and then transferred to inland hospitals . Within the Annexe level were dormitories , kitchens and mess rooms . A statue of Admiral Sir Bertram Ramsay was erected in November 2000 outside the tunnels in honour of his work on the Dunkirk evacuation and protecting Dover during the Second World War . If they were being attacked they would have to move quickly as the enemies were just nine minutes away from Dover by plane . There are over three miles of these Tunnels going deep down into the chalky cliffs , some still undiscovered . There are tunnels that are far too dangerous to walk down . Full information about these tunnels is not due to be released until 2020 - 2025 . The castle today . Dover Castle is a Scheduled Monument , which means it is a " nationally important " historic building and archaeological site that has been given protection against unauthorised change . It is also a Grade I listed building , and recognised as an internationally important structure . The castle , secret tunnels , and surrounding land are now owned by English Heritage and the site is a major tourist attraction . The Lord Warden of the Cinque Ports is officially head of the castle , in his conjoint position of Constable of Dover Castle , and the Deputy Constable has his residence in Constable ' s Gate . The Princess of Wales ' s Royal Regiment Museum is located in the castle . Between 2007 and 2009 , English Heritage spent £2 . 45 million on recreating the castle ' s interior . According to figures released by the Association of Leading Visitor Attractions , nearly 350 , 000 people visited Dover Castle in 2010 . Churches and chapels within its walls . Royal chapel . Within the keep , dedicated to Thomas Becket . St Mary in Castro . Saxon church , rebuilt in the Victorian era . External links . Images