DescriptionSleaford Castle is rare in being one of only three enclosure castles in Lincolnshire, and one which was both constructed and maintained under episcopal control. As a primarily administrative rather than military establishment it includes examples of distinctive structures, such as the manorial barn and constable's house, rarely associated with this type of monument. The remains of the castle survive well as a series of substantial earthworks and buried features which have never been excavated, suggesting the survival of structural features, artefacts and ecofactual deposits; in particular, waterlogging in the area of the moats will result in a high level of survival for organic remains. Diverse features are evident which, as a result of detailed historical research, are quite well understood. The remains represent a limited period of occupation and are relatively undisturbed by later activity; they will thus preserve valuable evidence for the construction and use of the castle, and contribute to our knowledge of medieval society, technology and economy. As a monument open to the public, Sleaford Castle also serves as an important recreational and educational resource.
The monument includes the remains of Sleaford Castle, an enclosure castle built in the early 12th century by Alexander, Bishop of Lincoln. Following a brief period of surrender to King Stephen in 1139 it was held by successive bishops for over 400 years, serving as an administrative centre for the episcopal estates in the Sleaford area. In the 15th century it was partially rebuilt by Bishop Alnwick, and in 1547 was transferred by Bishop Holbeach to Edward, Duke of Somerset. After this date it became a source of building materials and was progressively dismantled. In 1720 parts of the walls and towers were still standing; now the only fragment of masonry surviving above ground is part of the north eastern corner tower. The monument includes the standing remains of this tower and the earthworks and buried remains of the remainder of the castle.
Sleaford Castle is situated on the edge of the medieval parish of New Sleaford about 500m south west of the town centre. It is surrounded on all sides by low lying land, formerly waterlogged, including part of Sleaford Fen. The castle was built in this area of wet land by constructing raised earthwork baileys surrounded by water channels. The remains of the castle take the form of a series of substantial earthworks, including three raised areas: a large L-shaped outer bailey which was defended solely by water; a quadrangular inner bailey, defended by both water and a curtain wall; and a broad outer bank of linear form. The earthwork remains of these features and the moats which surrounded them occupy a roughly rectangular area on the south bank of the Nine Foot River.
The outer bailey is approached from the north western corner of the monument along a raised trackway, on the site of a former bridge, representing the original entrance to the castle. The outer bailey, which is of L-shaped plan, occupies the south western half of the monument; the western arm is approximately 55m long, the southern 60m, and both are between 15m and 20m in width. In the outer bailey are the earthwork and buried remains of agricultural and domestic buildings associated with the castle's function as the centre of a manorial estate. Principal among these are the remains of the manorial barn, a large rectangular structure aligned roughly east-west in the southern part of the bailey. The walls are visible as low earthworks defining an area nearly 50m long and over 15m wide. Documentary sources of the 14th to 16th centuries record the storage here of produce from the episcopal estates. Adjacent to the north east of the barn is a circular depression 1m deep surrounded by buried walls 0.5m high; this is believed to represent the remains of a circular dovecote, also known through documentary sources. Attached to the west side of the barn are the buried foundations of a smaller rectangular building approximately 20m long and 10m wide, believed to be the remains of a byre. In the western part of the outer bailey are further slight earthworks believed to represent the hall of the constable, who managed the castle on behalf of the bishop, and associated outbuildings such as stables.
The outer bailey is surrounded by the remains of two moats which were fed from the river to the north. On the south and west sides are the remains of the outer moat, a linear depression up to 30m wide and 2m deep. It survives in two parts: the southern arm, now dry, lies in the south eastern part of the monument; the western arm, also dry, is now occupied by public play equipment which is not included in the scheduling although the ground beneath it is included. The two arms of the moat formerly met at the south western corner of the outer bailey in an area outside the monument now occupied by the railway. On the north east side of the outer bailey are the remains of the castle's inner moat, also L-shaped. It is a dry, flat-bottomed depression up to 20m in width. Both the outer and inner moats are linked on the north to the earthwork remains of a further moat, constructed on the course of the river, which survives as a dry depression about 10m wide and stands up to 1.5m above the modern river channel which cuts along its northern edge. In the eastern part of the monument the outer and inner moats are linked to a linear moat aligned north-south, about 20m wide and still partially water filled, through which they drained back into the river.
In the northern part of the monument, surrounded by moats, are the remains of the castle's inner bailey. It is reached from the northern end of the outer bailey by a raised trackway which crosses the inner moat on the site of a former bridge. The inner bailey occupies a quadrangular area, approximately 80m by 60m, around the edge of which are the earthwork and buried remains of a curtain wall; deep linear trenches indicate where the limestone was robbed for reuse in the post-medieval period. In the north western part of the inner bailey, at the approach from the outer bailey, are the remains of the outer gatehouse, including two square depressions representing ground floor chambers, one on each side of the curtain wall. The outer gate is known through documentary sources to have had two portcullises. Also along the curtain wall are the earthwork remains of mural towers; at the north eastern corner is a large piece of standing masonry, partly fallen inwards and supported by two concrete pillars, which has been interpreted as part of a corner tower. The area enclosed by the curtain wall is divided into two rectangular courts by the earthwork remains of a further wall, at the north end of which are the earthworks of two substantial chambers, one on each side of the wall; these are believed to represent the inner gatehouse, also known through documentary sources. The area to the west of the dividing wall is otherwise mainly level and represents an outer court, largely open apart from some ancillary buildings such as the brewhouse. The area to the east of the wall contains a substantial series of earth covered walls and partially infilled depressions representing the remains of the main buildings of the castle, including the keep and chapel, and their basement storage chambers.
On the eastern edge of the monument, separated from the inner bailey by a moat, is a broad linear bank about 10m wide and 110m long. The top of the bank is flat and stands about 1m above the moat on its western side and 2m above the modern drain on the east. This bank, which forms an integral part of the defended earthworks of the castle, is interpreted as the site of the castle orchard or fruit garden described in documentary sources. (Scheduling Report)
Withoute the towne of Sleford standith west south west the propre castell of Sleford, very welle maintaynid: and it is cumpasid with a renning streme dimming by a cut oute of a litle fenne lying almost flatte weste againe it.
The gate house of the castelle 2. porte colices.
There is an highe toure in the midle of the castelle, but not sette apon {any} hille of reisid yerth.
The vaultes of the castelle by the ground be fair. (Leland)
although low lying, the site was eminently defensible. It was protected by the river to north, east and south, and a fen to the west, and the only approach was by the present causeway with access from West Gate. Writing in the mid twelfth century, Henry of Huntingdon claimed that Sleaford Castle was every bit as massive and magnificent as Newark Castle, but apart from a record of the expenditure of eight marks and 40d on repairs in 1215 (Pipe Roll, 102), there are no references to the earliest structures on the site. (Roffe)
