Planning to Restore the Marlborough Mound

Wiltshire Council Planning Application Reference

PL/2025/01126

Site Address
Castle Mound, Marlborough College, Bath Road, Marlborough, SN8 1NW

Proposal
To enhance the setting of the Castle Mound by demolition of structures which partially cut into the West side of the Mound, to provide an opportunity for further archaeological research to be carried out as and when the structures are cleared and finally to put a new curved stone-faced revetment to support the Mound.

Archaeological Summary

Tucked away in the private grounds of Marlborough College in Wiltshire (NGR SU 18325 68684) stands Marlborough Mound, a remarkable earthwork rising to 19 metres and covering a basal area of approximately 0.6 hectares. This Scheduled Monument (NHLE 1005634) holds exceptional national importance as the second-largest surviving prehistoric mound in Britain, surpassed only by the iconic Silbury Hill some 8 km to the west.

The Late Neolithic ‘Super-Mounds’ of Wiltshire

Core samples taken in 2010–11 and radiocarbon dated by Jim Leary (English Heritage) demonstrated that the mound was originally constructed in the Late Neolithic period, with dates centring on c. 2400–2300 BC. Silbury Hill (c. 39–40 m high, volume c. 250,000–300,000 m³) remains unparalleled – the largest artificial prehistoric mound in Europe. The Marlborough Mound, roughly contemporary with Silbury, is unequivocally the second-largest extant example in the United Kingdom. No other surviving Neolithic mound approaches its scale.

A third major mound once existed within Marden Henge (also known as Hatfield Barrow) in the Vale of Pewsey, about 10 km south of Silbury. Eighteenth- and nineteenth-century accounts describe it as a substantial conical earthwork, possibly up to 15 m high, but it was almost completely levelled by ploughing in the early nineteenth century; only a low rise now remains. Thus, among monuments that still dominate the landscape today, Marlborough indisputably holds second place behind Silbury.

These three great mounds – Silbury, Marlborough, and the lost Marden/Hatfield example – appear to form a distinct cluster confined to the river valleys of the upper Kennet and Avon during the later third millennium BC. Their purpose remains one of British prehistory’s enduring enigmas: none has yielded a burial, and all required astonishing communal effort over generations.

Later History

Shortly after the Norman Conquest the prehistoric mound at Marlborough was reused as the motte of a major royal castle. Kings from Henry I to John held court here, and a deep motte ditch (later adapted into a post-medieval canal) encircled the base.

By the seventeenth century the castle lay in ruins, and the mound was transformed into an elaborate garden feature for the Marquesses of Hertford. A sweeping spiral path was cut into the slopes, leading to a summit summerhouse, while a spectacular water-filled grotto was excavated into the north-western foot – vividly depicted in William Stukeley’s 1723 engraving.

When Marlborough College acquired the site in 1843 the mound became the centrepiece of its landscaped grounds. Early twentieth-century service buildings (a carpentry workshop, toilets, and plant room) were unfortunately built against the north-western base, necessitating the removal of a wedge of the mound and leaving a near-vertical section through its stratigraphy.

The Current Restoration Project

In 2024 Wessex Archaeology produced a detailed Historic Environment Desk-Based Assessment (ref. 295580.01) to support Marlborough College’s proposal to demolish these incongruous early twentieth-century structures and reinstate the original curved profile of the mound.

Key findings from the assessment and subsequent updates:

• Neolithic deposits are unlikely to survive beneath the building footprints owing to their construction, but the exposed section offers a rare opportunity for controlled archaeological recording.
• Good potential exists for surviving traces of the medieval motte ditch/moat and the post-medieval canal and grotto.
• Removal of the modern buildings will cause no harm to the Grade II Registered Park and Garden or to any listed buildings within the College; indeed, reinstating the mound’s form will greatly enhance key views across the grounds.
• By late 2025 planning permission and (presumably) Scheduled Monument Consent have been granted, and preparatory works are under way ahead of full restoration.

The project, supported by the Marlborough Mound Trust, represents an exemplary case of heritage-led regeneration: erasing insensitive twentieth-century alterations, repairing the monument’s silhouette, and enabling fresh archaeological insights into this enigmatic Neolithic giant.

Significance

Marlborough Mound encapsulates four principal phases of interest:

1. A major Late Neolithic ceremonial mound (c. 2400 BC) – second only to Silbury among surviving examples.
2. The motte of a high-status Norman royal castle (eleventh–fourteenth centuries).
3. An ambitious seventeenth–eighteenth-century garden mount with spiral walk and grotto.
4. The cherished landscape focus of one of England’s foremost public schools.

With the current restoration now approved and progressing, the mound is finally receiving the care it deserves after centuries of reuse and alteration. Once complete, it will stand proud once more – a restored Neolithic silhouette visible across the college grounds and a poignant reminder that some of Britain’s most extraordinary prehistoric monuments still hide, quite literally, in plain sight.