The monument comprises the remains of a motte associated with an Anglo-Norman timber castle likely to date to the 12th or 13th century AD. It is visible as a substantial mound located in a prominent position overlooking the Gryfe Water which flows around 40m to the north-west. The monument lies at around 80m above sea level and offers long views to the east and south. The confluence of the Green Water and the Gryfe Water lies around 320m to the south-west.
Today the remains of the castle are visible as a large earth mound, approximately circular on plan, measuring around 24m in diameter at its base and narrowing to 14m E-W by 13.2m transversely at its summit. The mound has a flat top and stands around 4m higher than the surrounding land on the W side and 2m higher on the E side. A small depression is visible near the centre of the summit.
The area to be scheduled is sub-circular on plan, to include the remains described above and an area around them within which evidence relating to the monument's construction, use and abandonment may survive, as shown in red on the accompanying map. To allow for their maintenance, the scheduling specifically excludes the above-ground elements of a telegraph pole sited north-west of the motte and the above-ground elements of a post-and-wire fence with gate that surrounds the motte.
Statement of National Importance
The monument's cultural significance can be expressed as follows:
The motte survives in excellent condition, although it is clear that there has been some limited disturbance in the past. There is a record that a mound at Denniston was excavated in 1894 and found to consist mainly of clay. The excavators cut a small trench 4 feet wide and found a row of boulders lying on a layer of ash about 4 feet below the surface, continuing down to natural ground level. The hollow visible on the top of the motte may derive from this investigation. Despite this limited intrusion, the monument has good field characteristics and the motte retains a good proportion of its estimated original shape, extent and structure. The motte is likely to preserve evidence of its construction, use and abandonment phases and may seal evidence for settlement or other activity that predated it. There is high potential for the survival of evidence for timber buildings and upstanding defensive works, both on the motte itself and in the surrounding area. Buried layers or cut features may contain important palaeoenvironmental evidence that can help us to reconstruct the diet and economy of the inhabitants and the nature of the immediate environment when the site was built and in use. The lack of evidence for stone buildings on the site suggests it was abandoned relatively early, enhancing the likelihood that archaeological remains of the timber castle may be well preserved. Researchers who visited the site in 1992 reported the discovery of a copper counting piece dating to the 15th to 16th centuries and a sherd of medieval pottery; they interpreted these items as deriving from occupation of the motte after it had ceased to be a defended structure. This suggests the potential for complex multi-period buried remains to exist.
This is one of over 300 fortified earthworks in Scotland dating probably from the 12th or 13th centuries. Many timber castles were associated with the establishment of Anglo-Norman lordships during and after the reign of King David I. They played a role in the consolidation of state power and the development of centralised authority, representing the fortified dwellings of an immigrant population and the introduction of a European model of land tenure and feudal obligations. The role of these fortified settlements was symbolic as well as functional, marking and protecting the lands of emerging lordships and the route ways through them. Timber castles are most numerous between the Clyde and the Solway, but there are also examples along other main route ways, often by significant water courses, such as those north of the Forth in eastern Scotland and stretching up to and including the Moray coast. Other examples survive in Caithness, Argyll and the Highlands. They are comparatively rare monuments in the former county of Renfrewshire, though potential examples are known at Pennytersal in Kilmacolm parish, at Castle Hill (Bridge of Weir) in Kilbarchan parish, and at Lochwinnoch, Renfrew and Eaglesham.
Many mottes were accompanied by baileys, defended outer courtyards that housed buildings and activities that could not be accommodated within the limited space on top of the artificial mound. There is no clear field evidence for man-made defences associated with the motte at this site, but it is very probable that associated buildings and ancillary structures existed. The timber castle that would have stood on the motte almost certainly acted as a manorial estate centre rather than simply a high status dwelling, making it probable that associated buried archaeological remains survive in the surrounding landscape. However, the motte was only the first of a series of estate centres in this vicinity. It was superseded first by Duchal Castle, to the west, and then by Duchal House, built in 1768 but incorporating elements dating to 1710. Archaeological remains associated with the motte and later estate centres may preserve evidence for the nature and chronology of the transition between them, allowing the potential for future researchers to address issues such as whether occupation was continuous or interrupted. The estate centre would have been part of a pattern of dependent settlements. The standing structures of a farm at South Denniston survived until the 20th century and are now visible as earthworks located around 75m ESE of the motte. The remains of a stone retaining wall lie immediately south of the motte and probably represent part of the field system associated with South Denniston.
The motte is depicted on 19th century maps that also show the former farm buildings at South Denniston. People in the past were aware of the motte, but did not know its precise date or function. Local tradition holds it to be the site of a Roman watchtower.
The monument is of national importance because it has an inherent potential to make a significant addition to the understanding of the past, in particular the construction and function of medieval strongholds. It retains a significant proportion of its field characteristics and is a well-preserved example of it class, with little sign of later disturbance other than limited antiquarian investigations. From it we can learn much about medieval castle construction, as well as the wider control of land and route ways in SW Scotland. Its importance is enhanced because it can be compared with later estate centres to the west, and can support analysis of the transition from timber to stone castles in Scotland. The loss of this example would significantly diminish our future ability to appreciate and understand settlement and land tenure in medieval Scotland.