The medieval ringwork and baileys at Castle Hills Wood survive well as a series of earthwork and buried deposits. Documentary research and archaeological survey mean that the site is quite well understood. The artificially raised banks will preserve evidence of land use prior to their construction. Its strategic position and later fortifications demonstrate its continued importance as a feature of the wider medieval landscape. As a high-status residence it contributes to our understanding of the social, economic and military activities of a particular component of medieval society.
The monument includes the medieval ringwork and baileys known as Castle Hills. Located in Castle Hills Wood on a west-facing escarpment overlooking the Trent valley, it is thought to date from the late 11th or mid-12th century. In 1086 Thonock was held by Roger of Poitou and around 1115 by the Count of Mortain. The site, which was referred to as the 'castle of Gainsborough', was granted by King Stephen to William de Roumare, Earl of Lincoln by 1146. In the late 12th and 13th centuries it became an important residence, notably of Edmund Earl of Cornwall, brother of Edward I, and was the centre of a barony. The site remained in residential use into the 15th century and the manor remained a holding of the Duchy of Lancaster until 1563, by which time it had been abandoned.
The monument takes the form of a ringwork with banked and ditched baileys adjoining it to the north and south and a steep scarp to the west. The central area of the ringwork is roughly circular in plan, measuring approximately 20m in diameter, and includes a hollow thought to represent the location of buried building remains such as a hall. The central area is enclosed by a bank and external ditch. The bank measures up to 10m in width and is more pronounced on the southern side of the central area. The ditch is steep-sided, measuring 15m in width, and is also more pronounced on the southern side of the ringwork. Additional defence was provided by another steep sided ditch, up to 5m deep, embanked on both sides, which encloses the southern half of the ringwork.
The northern side of the ringwork is enclosed by a bailey believed to be contemporary with the ringwork. The bailey is semi-circular in plan, the enclosed area measuring approximately 80m east to west, and is surrounded by a ditch with an internal bank. The bank and ditch are more pronounced on the eastern side of the bailey. A narrow entrance at the south east corner of the northern bailey is thought to represent an original access point, while mounds adjacent to the entrance are thought to be the tower foundations of a defensive gateway.
The southern bailey adjoins the south and east sides of the ringwork and is thought to represent a subsequent phase of defensive work. The southern bailey is kidney-shaped in plan, and the enclosed area measures approximately 140m north east to south west and is surrounded by a deep ditch with a high internal bank standing up to 5m above the bottom of the ditch. Mounds at the edge of the bailey are thought to represent further tower foundations. A small ditch and bank leads to the south from the south west corner of the bailey. The area immediately to the west and south west of the southern bailey is marked by a series of mounds and hollows thought to represent quarrying for gypsum, an industry associated with the manor during the 14th century. The western boundary of the monument is marked by an artificially enhanced west-facing scarp. (Scheduling Report)
The site is notable as an early military stronghold, a lordly residence and a major estate centre. The tactical and strategic position of the castle is very strong. This overtly military aspect, though again significant in the mid 12th century, perhaps makes it likely that the origin of the castle in its present form belongs to the immediate post-1066 period. On the other hand it is also possible that the castle was erected or at least enlarged or altered in the mid 12th century. In 1086 Thonock was held by Roger of Poitou and around 1115 by the Count of Mortain. It seems likely that the 'Castle of Gainsborough' which was granted to William de Roumare, earl of Lincoln, by King Stephen probably in 1142, is to be identified with this site. Only in the late 12th or 13th century, as part of the Honour of Lancaster, does the site appear to become a principal residence and the centre of a barony. The earthworks consist of a substantial ringwork flanked on both the north and south by outer baileys of more than one period. The first phase was probably the ringwork and the north bailey. The former consists of a steep-sided circular rampart standing up to 5.5m above the bottom of the surrounding ditch and with traces of internal buildings. The tongue-shaped bailey is surrounded by a ditch, reinforced on the east by a broad inner bank standing 4m above the bottom of the ditch, with a possible narrow entrance at the north-east. Additional defensive earthworks along the south side of the ringwork, consisting of a crescentic outer ditch flanked by banks 3 to 4m high, may perhaps be contemporary, or may belong to the second phase of development. This second phase was the addition of the south bailey, a kidney-shaped area enclosed by a massive bank 2.75m high and 5m above a wide outer ditch. Irregularities on the bank may reflect later damage, but could have been caused by the removal of masonry structures, and mounds at the north-west and north-east corners of the bank could represent the sites of former towers or turrets. (Lincolnshire HER ref, Everson, Tayloer and Dunn 1991)
A medieval ringwork and baileys known as Castle Hills, located in Castle Hills Wood. It is thought to date from the late 11th or mid 12th century, and the site may have been location of King Sweyn of Denmark's winter camp, known as "Danish Camp". The monument takes the form of a ringwork with banked and ditched baileys adjoining it to the north and south. The central area of the ringwork is roughly circular in plan, measuring 20 metres in diameter, and includes a hollow thought to represent the location of buried building remains such as a hall. The central area is enclosed by a bank and external ditch. The bank measures up to 10 metres in width and the steep-sided ditch measures 15 metres in width. The northern side of the ringwork is enclosed by a bailey and believed to be contemporary with the ringwork. The bailey is semi-circular in plan, the enclosed area measuring 80 metres east to west, and is surrounded by a ditch with an internal bank. The southern bailey adjoins the south and east sides of the ringwork and is thought to represent a subsequent phase of defensive work. The southern bailey is kidney-shaped in plan, and the enclosed area measures 140 metres north east to south west and is surrounded by a deep ditch with a high internal bank. (PastScape)