Lincoln Castle located in Lincoln, England and was built during the late 11th century by William the Conqueror on the site of a pre-existing Roman fortress.
When William the Conqueror defeated Harold and the English at Hastings on the 14th October 1066 he continued to face resistance to his rule in the north of England. For a number of years William's position was very insecure and in order to project his influence northwards to control the 'Danelaw' he felt it necessary to construct a number of major castles in the north and midlands of England. It was at this time that the new King built major castles at Warwick, Nottingham and York. After gaining control of York, the Conqueror turned southwards and arrived at the Roman and Viking city of Lincoln. When William reached Lincoln he found a Viking commercial and trading centre with a population of 6,000 to 8,000. The remains of the old Roman walled fortress located 60 metres (200 ft) above the countryside to the south and west, proved an ideal strategic position to construct a new castle. A castle here could guard several of the main strategic routes and form part of a network of strongholds of the Norman kingdom, in Danish Mercia, roughly the area of the country that is today referred to as the East Midlands, to control the country internally. Also it could form a center from which troops could be sent to repel Scandinavian landings anywhere on the coast from the Trent to the Welland, to a large extent, by using the roads which the Romans had constructed for the same purpose. Work on the new fortification was completed in 1068. It is probable that at first a wooden keep was constructed which was later replaced with a much stronger stone one.
Lincoln castle is a little unusual in having two mottes. To the south, where the Roman wall stands on the edge of a steep slope, it was retained partially as a curtain wall and partially as a revetment retaining the mottes. In the west, where the ground is more level, the Roman wall was buried within an earth rampart and extended upward to form the Norman castle wall. The Roman west gate which is on the same site as the castle's westgate, was excavated in the 19th century but collapsed on exposure.
During the English Civil War, Lincoln was on the frontier between the Royalist and Parliamentary forces. Military control of the city therefore changed hands numerous times. Many buildings were badly damaged. The early part of the war went well for the Royalists. That changed in the late summer and early autumn of 1643, when the Earl of Essex's army forced the king to finish the siege of Gloucester and then brushed the Royalist army aside at the First Battle of Newbury on the 20th September 1643, in order to return triumphantly to London. Other Parliamentarian forces won the Battle of Winceby, giving them control of Lincoln. Political manoeuvering to gain an advantage in numbers led Charles to negotiate a ceasefire in Ireland, freeing up English troops to fight on the Royalist side in England, while Parliament offered concessions to the Scots in return for aid and assistance.