The monument includes a moated preceptory and an associated fishpond situated beside the River Darent. The preceptory lies on a NNW-SSE orientated, sub-rectangular, artificial island measuring 185m by 120m. In the north western quarter of the island are the remains of the preceptory chapel, dating from the 13th century, incorporated within a later, 16th century residence, with 17th and substantial 18th and 19th century additions and alterations in brick. The residence is a Grade II* Listed Building. Documentary evidence suggests that the main period of medieval building took place around 1234, when Henry III is recorded as having ordered five oaks from Tonbridge Forest for the chapel roof. The chapel is a rectangular building, with external buttresses, constructed of flint rubble with ashlar dressings. It is lit by simple, lancet windows, several of which, along with the original doorway on the south eastern wall, have been blocked at a later date. Inside the chapel, on the ground floor at the eastern end of the south eastern wall, is a double piscina, or alcove, originally containing water basins. At the south western end is a further area of medieval walling which may represent the remains of a tower. Traces of further preceptory buildings may survive in buried form beneath the undulating ground which forms the modern gardens surrounding the residence. The island is surrounded on all four sides by a moat, the south western arm of which is formed by the River Darent. The northward flow of the river both feeds and drains the moat. The north western, north eastern and south eastern arms remain waterfilled and are between 5m and 8m wide. A modern sluice controls the flow of the river near the north western corner of the moat, and the banks of the river at this point are retained with modern brick walls. There is also a smaller modern sluice on the north western arm of the moat. The moat is bounded by retaining earthworks which survive particularly well on the north western and north eastern sides, taking the form of substantial linear banks up to 2m high and 12m wide. Access to the island is provided by a Grade II Listed, 19th century, brick-built bridge situated near the northern end of the south western arm of the moat. Two modern footbridges span the north eastern arm and the north western corner of the moat. The preceptory is thought to have gone out of use by 1338, after which time it was used as a residence. Amongst its later occupants were Abraham Hill, a founder member of the Royal Society, who lived at the manor house between 1667 and 1721, and, between 1757 and 1776, Edward Hasted, the historian, who carried out many of the 18th century alterations to the buildings. The preceptory and its surrounding land were given to the National Trust by Sir Stephen and Lady Tallents in 1943. To the south west of the moat on the opposite river bank are the earthwork remains of a narrow, rectangular fishpond originally fed with freshwater by the river. This is a slightly sunken, marshy area of ground 146m long and 12m wide. The residence of which the chapel forms a part, and the main, 19th century bridge across the south western arm of the moat, are excluded from the scheduling as they are considered to be more appropriately protected by their listed status. All modern garden walls, fences, greenhouses and outbuildings situated on the island, the modern sluice and retaining walls near the bridge and the two modern, wooden footbridges are also excluded from the scheduling, although the ground beneath all the above features is included. ASSESSMENT OF IMPORTANCE A preceptory is a monastery of the military orders of Knights Templars and Knights Hospitallers (also known as the Knights of St John of Jerusalem). At least one preceptory of the Knights of St Lazarus is also known to have existed in England. Preceptories were founded to raise revenues to fund the 12th and 13th century crusades to Jerusalem. In the 15th century the Hospitallers directed their revenue toward defending Rhodes from the Turks. In addition, the preceptories of the Templars functioned as recruiting and training barracks for the knights whilst those of the Hospitallers provided hospices which offered hospitality to pilgrims and travellers and distributed alms to the poor. Lazarine preceptories had leper hospitals attached. Like other monastic sites, the buildings of preceptories included provision for worship and communal living. Their most unusual feature was the round nave of their major churches which was copied from that of the Holy Sepulchre in Jerusalem. Indeed their use of such circular churches was unique in medieval England. Other buildings might include hospital buildings, workshops or agricultural buildings. These were normally arranged around a central open space, and were often enclosed within a moat or bank and ditch. From available documentary sources it can be estimated that the Templars held 57 preceptories in England. At least 14 of these were later taken over by the Hospitallers, who held 76 sites. As a relatively rare monument class, all sites exhibiting good survival of archaeological remains will be identified as nationally important. Archaeological remains of the preceptory of the Knights Hospitallers at Sutton-at-Hone survive well and it is rare for standing remains to survive in monuments of this class. In addition, it will provide evidence relating to the occupation of the site and the nature of the surrounding environment. The waterfilled moat and the associated fishpond provide ideal conditions for the survival of organic remains.