Scheduled Ancient Monument: Moated site known as Offton Castle (SF57)

Medieval moated site known as Offton Castle surviving as earthworks and buried remains. The moated site at Offton is a homestead moat, thousands of which were constructed mainly in the C13 and C14, although this one differs in its curiously raised platform. No comparable examples have been identified, making it a highly unusual survival. The first reference to a ‘castle’ in Offton dates to around 1200, which in turn refers to William de Ambli holding a castle here against Adam Cockfield of Lindsey Castle, 12km to the west, during the Anarchy of Stephen’s reign, 1138-53. This would be early for a homestead moat, and strongholds thrown up during this period were usually circular or curvilinear. It has been suggested that Offton Castle may have been adapted from such a motte and, whilst no evidence for this has been seen, it might explain the height of the island, potentially increasing its significance. Buried evidence for this precursor would add further to its rarity. An Ordnance Surveyor’s sketch map of 1799 shows the moat (and the farm buildings to its north) to lie within a large rectangular enclosure approached by lanes from the east and north. Although drawn at a small scale and rough in its level of detail it clearly shows the square moat and island, labelled as ‘Ofton Castle’. The published 1837 Ordnance Survey (OS) 1-inch to 1-mile map is similar but a little more detailed. It again shows the whole complex within a large sub-rectangular enclosure approached from the east and north (and perhaps west), with ‘Offton Castle Farm’ labelled, as well as the ‘Castle’ in gothic script indicating an antiquity. The square moat and island are clear and there appears to be a channel running south-east from the south-east corner of the moat. The depiction of the moat on the OS 6-inch and 25-inch to 1-mile maps published in 1885 differs little from later editions and shows the moat much as seen today. The site has not been excavated but the interior may contain buried remains of buildings and archaeological deposits associated with the site. PRINCIPAL ELEMENTS The earthworks of the moated site include a wide, water-filled ditch enclosing an almost square area about 57m by 62m, which is raised about 2.4m above the surrounding ground. DESCRIPTION The site lies at about 67m Above Ordnance Datum (AOD) on a broad spur projecting north-east from an undulating plateau to the south and west at about 70m AOD. It forms part of the garden to Castle Farm. The moat is water-filled and approximately square. The moat arms vary a little in length, the north measuring about 87.3m, the east 88.5m, the south 87.8m and the west 90.3m. The south-west and north-east corners are slightly acute and the north-west and south-east corners slightly obtuse creating an irregular diamond shaped moat. The moat arms are generally quite uniform widths and the moat island closely reflects this plan. The top of the moat island measures up to 48.5m north-south (above the east arm), by 47.2m east-west (above the north arm). Its surface is generally level with a slight rise to the south and faint scarps suggestive of buried structural remains, though coppice stools and other trees may be responsible for the vague features. Its surface is about 2.5m above the surrounding ground levels, apparently achieved by throwing the material excavated from the moat up onto the island. To the east, south and west the island has steep scarps falling about 4m directly into the moat. They are generally straight and uniform apart from some evidence for historic tree throws. Some fairly large trees are growing on these scarps. The northern side of the island has a long, steep sided, slightly irregular hollow cutting south into the island which probably represents a collapse or robbing of whatever stood on the moat island. A 1532 reference to stone being taken from the castle supports this theory and several moulded stones were noted in the south wall of Castle Farmhouse. Access to the moat is limited due to vegetation but as far as can be seen the east, south and west moat arms are generally straight sided and uniform widths, with symmetrically angled internal and external scarps. Internal corners are sharp and well defined, the external corners a little rounded. At the south-west corner, where the external ground level is lowest, an embayment projects south from the moat, and south of this is an open hollow. This seems to mark a former outlet, and the 1837 1-inch to 1-mile Ordnance Survey map seems to show a short surface drain here. The northern moat arm is rather different to the others. As already described, the south side curves south where there is a hollow in the north side of the moat island. To the east is a footbridge allowing access to the island. Short earthwork spurs to north and south shorten the length of the bridge required. This is a relatively modern feature, though a bridge in this position is shown from the 1880s onwards. To the west of this the moat appears to have its original form though there is a broad hollow to the north which is suggestive of erosion, perhaps the result of poaching by livestock accessing the moat. To the east, the northern side of the moat arm is steeper than seen elsewhere. EXTENT OF SCHEDULING: the scheduled area includes the complete, approximately square shape of the platform and moat, marked on the attached map, and includes a 5m buffer zone, which is considered necessary for the support and preservation of the monument. EXCLUSIONS: the scheduling excludes any modern road or track surfaces, walls or fences, signage, or drain covers that fall within the site, though the ground beneath them is included.