Marlborough Mound

Summary

A Neolithic monumental mound constructed in the second half of the 3rd millennium BCE; reused and modified as the motte for Marlborough Castle, from at least 1175 to the mid 14th Century; then adapted as a garden prospect mound in the later 16th Century or early 17th Century.

Reasons for Designation

Marlborough Mound, a Neolithic monumental mound, is scheduled for the following principal reasons:

* Period: monumental mounds are one of a relatively small number of monument classes known from the late Neolithic period, although their function and purpose is not yet fully understood;

* Rarity: Marlborough Mound is one of a group of very rare monuments; only four more or less certain monumental mounds are currently known;

* Potential: contains important information about its construction, dating and its original purpose, which is yet to be established, as well as additional information about the subsequent phases of its alteration and re-use;

* Survival: for the substantial size of the surviving earthworks, despite later interventions and alterations associated with the medieval motte castle and C17 prospect mound;

* Group value: with Silbury Hill, which lies only about 8km to the east, and is another, larger example of this rare monument type, contemporary with the Marlborough Mound;

* Documentation: the motte castle and prospect mound phases of the monument are well documented, and this adds to our understanding of how the monument was used in its later phases.

History

A monumental mound is a large conical-shaped mound of earth and stone, of prehistoric date, often carefully constructed with internal revetments, surrounded by a substantial quarry ditch and in some cases an outer bank, the whole structure being in excess of 150m in diameter. Most lie near to henge enclosures. Monumental mounds are usually recognized as up-standing earthworks or, when heavily denuded, from antiquarian sources. Monumental mounds may potentially be confused with large round barrows of various classes (especially bowl barrows) but these rarely exceed 45m in diameter and are therefore generally rather smaller than the monumental mounds. Other sources of confusion include the mottes of medieval motte-and-bailey castles and prospect mounds in post-medieval gardens. These can usually be distinguished by their fresh and recent appearance and the presence of related components. Some monumental mounds were, however, reused as mottes or prospect mounds in recent times which means that great care must be taken in the identification and classification of these sites. Monumental mounds appear to have been ritual or ceremonial monuments of late Neolithic date closely related to the henge and henge-enclosure traditions of southern England.

A motte castle is a large conical or pyramidal mound of soil and/or stone, usually surrounded by either a wet or dry ditch, and surmounted by a tower constructed of timber or stone. In many cases the mound may have been further strengthened with palisades and revetments which will no longer be visible but may be revealed by archaeological excavation, as may other features such as bridges, gateways, and steps. Motte castles are usually fairly easy to identify as field monuments, although the mottes can sometimes be wrongly attributed, as excavation has shown at Pontesbury (mutilated ringwork with possible traces of a bailey), and Puriton (slagheap). Sometimes large barrows, windmill mounds, and garden landscape features have been confused with the remains of motte castles. It is possible that some mounds may have been used for more than one of these purposes; the siting of the mound can be significant as the mottes often dominate a road, river crossing, or settlement. Close attention to historical documents can also be important in recognising and authenticating motte castles.

Marlborough Mound is one of a rare class of monuments known as Neolithic monumental mounds, of which only four examples have so far been identified with any certainty, the best-known of which is Silbury Hill, located 8.3km to the west, at West Kennett. The Marlborough Mound shares the same profile as Silbury Hill, but is only around half its height. From the early C19 there had been speculation that the mound might have prehistoric origins; Richard Colt Hoare suggested this hypothesis in 1821, though in the absence of corroborating evidence, it remained a point of contention. In 1912, HC Brentnall, a schoolmaster at the college, published a history of Marlborough Castle, which included a summary of the available archaeological evidence. During the construction of a boiler house and its attendant chimney at the north-west side of the mound, six fragments of red deer antler were discovered within the chalk which makes up the mound, in a position suggesting that their inclusion could only date from its construction. The 1912 excavations, carried out when a portion of the edge of the mound was removed to allow the construction of some small buildings for plant, also showed that the original ground surface was alluvial, with charcoal and broken flint above. Excavations in 1955 uncovered medieval refuse on the old ground surface, including Norman pottery, supporting the theory that the mound was first constructed as a motte castle. Later surveys and analysis, including a RCHME survey in 1999, were inconclusive. Following extensive work on Silbury Hill, further investigation was undertaken in 2010 at Marlborough Mound as a possibly comparable site. This included core sampling through the entire depth of the mound into the ground surface below, and in the probable surrounding ditch. This investigation demonstrated with 95 per cent confidence that the mound was constructed in the second half of the third millennium BC: its construction began in 2580-2470 BC, making it broadly contemporary with Silbury Hill; it was completed 2300-2040 BC. The probable ditch surrounding the mound was also investigated, but with less conclusive results, indicating that there has been significant disturbance of the stratigraphy. A likely depth of 3m was recorded, but the width (up to 14.6m) is uncertain, and it was concluded that the ditch may have originated or at least been substantially altered in the post-medieval period, to create the water garden recorded in the C17.

The mound was re-used in the medieval period as a shell keep castle, which is well-documented. Excavations for building in 1936 found the footings for a curtain wall and the buttress for a shell keep, together with C12-C13 pottery. Marlborough was part of a royal borough which was visited often by sovereigns. There is no documentary mention of a castle prior to 1138, but it is thought significant that William I imprisoned Bishop Aethelfric of Selsey in Marlborough and that Henry I held an Easter Court there in 1110. Several charters were signed in Marlborough which implies the castle did already exist. The first definitive documentary record was in 1139 when it was held by King Stephen from the Empress Matilda. There was further building work during the reign of Henry II which included the ‘Great Tower’ and continued from 1175 to 1179. King John had the castle repaired and a ring wall built around the motte in 1209-1211. Henry III spent £2000 on works between 1227 and 1272 which included work on two chapels, the hall, the keep, two barbicans, a curtain wall, two bridges, gatehouse, and the Queen's apartments. From 1273-1369 it formed part of the Queen's possessions as her ‘Dower House’. However, by 1403 it had deteriorated significantly and subsequently remained neglected.

Speculation of this having once been part of a much larger castle with baileys was apparently fuelled by the discovery of a V-shaped profile ditch to the north of the motte in 2000, and it has long been believed that much of the bailey extended to the south, although the extent of this is not known. Resistivity survey of the garden areas to the south of the mound and possible ditch, outside the scheduled area, believed to be the site of the former bailey, was undertaken in 2015. This demonstrated the existence of structures in the area including a possible curtain wall and potential rubble spread from a tower, but does not indicate the full extent of the structures due to the constrained area of the survey site. A hypothetical reconstruction by Brentnall from the 1920s does not align with most of the survey results. Subsequent trial excavation in 2018-2019 confirmed the presence and character of walls in this area, but were not conclusive. Further doubt was cast on the Brentnall plan by an archaeological watching brief over the construction of service trenches in 2022, which found evidence of a mortar floor and walls in the area immediately south of the mound, where Brentnall had postulated a moat. A ground penetrating radar survey and more extensive excavation was subsequently carried out in the area of the Wilderness garden, which again uncovered the remains of a wall and floors, believed to be part of the bailey wall and attached structures, and part of what has been interpreted as a corner bastion. However, no medieval material from a sealed context was recovered during the excavation, so there is no confirmed date for these structures, and it is not possible to identify their extent.

By 1541 Marlborough Castle was ruinous, and a house probably occupied the site by then or soon after. Sir Francis Seymour constructed a new house on the site before 1621, probably set within formal gardens with the mound in use as a garden mount. In 1642, considerable damage was done to the site when parliamentary soldiers used the mount for defence purposes, and also in 1644, when Charles II took possession of Seymour's house and fortified it. Two years later, Seymour was allowed to rebuild his house, by then called Marlborough House. In 1654 John Evelyn visited him and noted the mount, which was certainly in use as a garden feature at that date, with the present winding path having been cut in to the mound, edged by hedging, and with some trees apparently planted at the summit. By 1664, a cistern with an octagonal banqueting house set over it had been constructed on the top of the mound, though the banqueting house had collapsed by the end of the century, to be replaced by a smaller octagonal summer house. In the early C18, under the ownership of Lord and Lady Hertford, further improvements were undertaken to the house and grounds at Marlborough. Illustrations by William Stukeley include a birds’ eye view of 1723, which shows formal gardens that include the mount with a canal encircling much of its base and continuing to the south on both sides, along with terraces, parterres, a wilderness immediately to the south of the mound over the site of the possible castle bailey, and various garden buildings. Sometime before 1726, Lady Hertford created a grotto at the base of the mount (Listed, Grade II), and subsequently, in the late 1730s, further improvements to the garden were undertaken which involved the widening of parts of the moat, the building of a ruinous arch, and the addition of cascades. In 2005, further excavations confirmed that the spiral path which winds its way up to the summit was in existence in 1654.

In the middle of the C18, Marlborough House was sold and became the Castle Inn, which in 1843 became part of Marlborough College (now C House NHLE 1273163). The canal encircling the northern half of the mound, still shown on the tithe map published in the 1840s, was filled in, leaving a modified section to the south-west by the end of the C19, used for bathing. Shortly after 1843 various new school buildings were constructed to the east of the mound, around Marlborough House. In 1883-1886 the new chapel of St Michael and All Angels was built to the north of the mount. In the inter-war years, the college grounds were expanded to the north-west of the mound. In the late 1930s a small formal garden was created to the south of the chapel. Further school buildings were introduced immediately to the south of the mount in the second half of the C20, partially covering the site of the former wilderness. Further buildings were constructed very close to the foot of the mound on the west and south-west sides, including over the former bathing pool. The remainder of the wilderness was retained as gardens. In the late C19, a water tank was installed at the summit of the mount, which appears to have been truncated slightly, though whether to facilitate the cistern which preceded the tank, or at an earlier date, is not clear; this was later removed, leaving a circular depression surrounded by an earthen bank. A small trial excavation has demonstrated that, despite the C20 disturbance, this bank retains material from the earlier phases of the mound’s use.

Details

PRINCIPAL ELEMENTS
A Neolithic monumental mound constructed in the second half of the 3rd millennium BCE; reused and modified as the motte for Marlborough Castle, from at least 1139 to the mid-C14; then adapted as a garden prospect mound in the later C16 or early C17.

DESCRIPTION
The monument includes a monumental chalk mound covered in grass, which stands over 18m high from the present ground surface; it has a basal diameter of 83m and its flattened top measures 31m across. On the summit is a deep, circular depression bounded by an earthen bank, about 15m across, which housed a C19 water tank, recently removed, though a number of scars remain, including a concrete base and concrete steps and access hatch. The sides of the mound are populated by a number of mature trees, and are also marked by the scars of previous interventions, including the site of a flight of concrete steps to the west of the grotto, rising to the top of the mound, which have since been removed. A spiral walkway just over 1.5m wide, dating from the C17, winds around the mound, encircling it four times before it reaches the flattened top; the level surfaces are covered in gravel and retained by a mixture of timber planks and metal edging strips. On the south side an early-C18 grotto (NHLE 1273151) was cut into the base of the mound, reached from the surrounding ground level by a short flight of three steps. The feature was reconstructed in 2000 – 2002. The structure is built from flint, with blind, arched window openings flanking a wide central opening, crenellated parapet and stone bands. The interior has a domed, vaulted roof and round-headed niche, all with shell decoration. On the east side, a small belvedere, formerly covered in shells, with a built-in seat, is cut into the side of the mound on one of the level areas created by the walkway. The base of the mound is partially surrounded by a sarsen stone revetment wall of varying numbers of courses, mainly to the east and north sides. Elsewhere, the edge of the mound is bounded by modern kerbstones or allowed to die away with no retaining boundary. On the north-west side, a notch is cut into the mound with a brick retaining wall, in which space a small brick boiler house has been inserted. The surrounding area, over part of the former ditch, is covered in tarmac.

The mound is closely bounded by buildings of various dates; to the south lies a small garden area over part of what might be the outer baileys and buildings associated with the motte castle.

EXTENT OF SCHEDULING
The site consists of a roughly circular area of approximately 93m diameter at the widest part, closely bounding the mound at ground level. At the present time (2025) there is insufficient evidence to demonstrate the survival of nationally important remains to the south, in the area which is believed to be the site of the medieval castle bailey, to justify including any of this area in the scheduling.

EXCLUSIONS
All posts, markers, and the surfaces of paths are excluded from the scheduling, though the ground beneath is included. The above-ground elements of the C18 grotto, which stands on the south side of the mound, are excluded, but the ground beneath is, however, also included.

Legacy

The contents of this record have been generated from a legacy data system.

Legacy System number:

WI 321

Legacy System:

RSM - OCN

Sources

Books and journals
Leary, J, The Marlborough Mound, Wiltshire. A Further Neolithic Monumental Mound by the River Kennet. in Proceedings of the Prehistoric Society, Vol. 79, (2013), 137-163
Barber, R, The Marlborough Mound: Prehistoric mound, Medieval castle, Georgian garden, (2022)

Other
Archeoscan: Report on Geophysical Survey at Marlborough Castle, Wiltshire (2015)
Marlborough Mount or Marlborough Mound: Wiltshire and Swindon Historic Environment Record SU16NE450
Archeoscan: Marlborough Castle – Archaeological Excavation at Marlborough College (MARL 18) (2018-19)
Wessex Archaeology: Marlborough Mound Phase 4 Investigations (2020)
Wessex Archaeology: The Mound, Marlborough College – Ground Penetrating Radar Survey Report (2017)
Wessex Archaeology: Marlborough College Generator and Cable Installation – Archaeological Watching Brief (2018)
Wessex Archaeology: Marlborough Mound, Marlborough College, Wiltshire – Historic Environment Desk-based Assessment (2024)
Archeoscan: Marlborough Castle - Archaeological Excavations at Marlborough College 2017 to 2022 (2022)
Archeoscan: Archaeological Watching Brief for Norwood to Wilderness Drainage Marlborough College (2022)

End of official list entry

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