Restoring Stonehenge: securing a Neolithic monument over 120 years

This autumn, specialists have been working to conserve some of the Stonehenge sarsens, the latest in a series of initiatives stretching back to the dawn of the 20th century. CA Editor Carly Hilts spoke to Heather Sebire to find out more.

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Visitors to Stonehenge in September may have noticed a strikingly modern addition to the Neolithic monument: a mobile scaffolding tower. This autumn has seen one of the most significant conservation projects to take place at the site in more than six decades, aimed at securing the stones against erosion as well as undoing some of the effects of well-intentioned but ultimately damaging repairs carried out more than half a century earlier.

The recent conservation works stemmed from two previous pieces of research: a laser survey of the monument, and a detailed engineerโ€™s report. The former initiative saw high-resolution scans undertaken in 2012, during the first comprehensive laser survey of Stonehenge. This was intended to help record and assess the condition of the stones, but also revealed that prehistoric graffiti that had first been identified at the site in the 1950s was much more extensive than previously thought. Some 71 previously unknown carvings of axe-heads resembling known artefacts from the Early Bronze Age (c.1750-1500 BC) were picked up during the survey, bringing the total at the site to 115, and doubling the number of similar motifs documented in Britain to-date (see CA 273). These scans were a vital tool, too, to help English Heritage, in whose care Stonehenge lies, to identify any cracks or other erosion to the stones.

Conservation begins on the Stonehenge lintels. Septemberโ€™s project represented the most significant conservation work carried out on the Neolithic monument in more than 60 years. Photo: English Heritage.

The other key piece of research was a study in 2018, led by Professor David Nash at the University of Brighton, which saw chemical analysis used to pin down where the Stonehenge sarsens were quarried. The sarsens, added to Stonehenge c.2500 BC in the third stage of the monumentโ€™s construction, make up most of Stonehengeโ€™s key features, including all 15 stones in the inner trilithon horseshoe, 33 uprights and lintels in the outer circle, and other outlying elements. Unlike the smaller bluestones, which have been traced to the Preseli region of west Wales (CA 366, 345, and 311), and the sandstone Altar Stone, which is from east Wales, the sarsens are rather more local in origin, having been traced to West Woods in the Marlborough Downs, about 25 miles north of Stonehenge (CA 367). Nashโ€™s research also gave English Heritage the chance to conduct a fuller examination of the stonesโ€™ state of preservation.

โ€˜At the same time as the scaffold was up for this chemical analysis, we took the opportunity to ask Historic England engineers to do a report on the stability of the stones, especially the horizontal lintels, as they hadnโ€™t been looked at in years,โ€™ explained Dr Heather Sebire, Senior Property Curator at Stonehenge. โ€˜We wanted to check that everything was OK, particularly in the light of the more extreme weather we have been having in recent years. The good news is that there was nothing structural that needed doing โ€“ we werenโ€™t worried the lintels were going to fall down or anything like that โ€“ but the report did highlight some problems associated with repairs from the 1950s and 1960s, when they used a very hard mortar that we wouldnโ€™t use today.โ€™

Dr Heather Sebire inspects some of the Stonehenge lintels with James Preston from Sally Strachey Historic Conservation. Photo: English Heritage.

The historical repairs particularly affected the joints between the lintels and their supporting uprights. These towering constructions represent an awe-inspiring feat of prehistoric engineering: with each sarsen measuring up to 9m in height and weighing up to 30 tonnes, they fit together using an impressively intricate system of protruding tenons and mortice holes, while the lintels themselves slot together using tongue and groove joints reminiscent of woodworking. However, when the stones had last been restored over half a century ago, many of these joins had been packed with hard mortar that is not breathable. As the material degrades over time, it leaves the stones vulnerable to damage caused by trapped moisture freezing and expanding within cracks, causing erosion.

To counteract this, English Heritage contracted specialists from Sally Strachey Historic Conservation to remove the old mortar and repack the joints with breathable lime mortar, which allows water to escape. Two conservators used a scaffolding tower to access the tops of the stones in order to complete this work, and they have also been examining the skyward surfaces of each of the nine lintels that are still in place, checking for any naturally formed holes that might be large or deep enough to form puddles. It is hoped that these efforts, combined with regular monitoring in the future, will allow the stones to withstand the forces of wind and weather for many years to come.

A history of restoration

The 1950s repairs were not the first efforts to secure Stonehengeโ€™s future. The story of restoring the monument begins at the start of the 20th century, when Stonehenge was owned by the Amesbury-based Antrobus family, on whose estate it stood. Although the stones had been accorded scheduled status in 1883, officially recognising their national significance, little had been done to preserve the site, and after more than 4,500 years of battering by wind and rain, the monument was in a rather ruinous state. The catalyst for action came on New Yearโ€™s Eve in 1900, when one of the stones collapsed. Amid the ensuing public outcry, Sir Edmund Antrobus commissioned restoration works. These were overseen by Professor William Gowland (1842-1922), an engineer and amateur archaeologist best known for his excavations in Japan, and the project saw Stone 56 โ€“ the tallest of the Stonehenge sarsens, and the sole surviving upright of the Great Trilithon that once stood at the head of the monumentโ€™s inner horseshoe โ€“ straightened and set in concrete.

Photographs of the restorations that took place at Stonehenge in the 1950s capture dramatic scenes of Neolithic stones being raised back into place โ€“ as well as attitudes to health and safety that are somewhat startling for modern observers. Photos: Historic England Archive

The year 1915 marked another dramatic change of circumstances for Stonehenge: Sir Edmund had died and, with the loss of his heir during the First World War, the Antrobus estate was auctioned off piece by piece. Stonehenge was Lot 15, sold for ยฃ6,600 to local barrister Cecil Chubb. The story goes that this was an impulse purchase intended as a gift for his (reportedly less than impressed) wife, but three years later the monument was presented to another new owner: the nation. It was an undoubtedly generous gesture (for which Chubb was knighted), but the gift itself was not in the best condition, and an assessment by the Office of Works revealed numerous points of concern. The following year, in 1919, another more ambitious restoration programme was launched, this time headed by Lieutenant-Colonel William Hawley, who also took the opportunity to carry out excavations at the site on behalf of the Society of Antiquaries. Focusing on the elements that the Office of Works deemed most in need of attention โ€“ notably Stones 1 and 2, and 29 and 30 โ€“ further sarsens were winched upright and set in concrete, while the fallen lintel capping Stones 6 and 7 was also raised back into place.

It would be decades before there were further interventions at Stonehenge, but engineers did return to the stones in the late 1950s and early 1960s, following on from excavations carried out by Professors Richard Atkinson and Stuart Piggott, and John F S Stone. This trio was preparing Hawleyโ€™s earlier findings for publication, but also carried out important investigations of their own. It was during this project that the first axe and dagger carvings were identified on some of the stones, but one of the most significant outcomes of the research was the recovery of charcoal from one of the Aubrey Holes. This was used to produce the first radiocarbon date ever established for Stonehenge. The result was not hugely precise, spanning 2123-1570 BC, but it was a breakthrough for the landmark, which had never before been scientifically dated.

Eight-year-old Richard Woodman-Bailey inspects diagrams prepared by his father, the chief architect of the last programme of Stonehenge restorations, in 1958. Photo: Historic England Archive.

The restoration efforts were equally significant, straightening and concreting several stones within both the outer circle and the inner horseshoe of sarsens, while a number of fallen bluestones were also re-erected at this time. These works had the advantage of rather more modern technology than had been available to their early 20th-century predecessors, including the use of a crane specially designed for moving aircraft. Even so, the weight of some of the larger stones, when combined with the purpose-built cradles used to support them, almost exceeded the craneโ€™s 60-tonne capacity. While great care was taken in raising the stones and guiding them back into place, though, health and safety for humans on site was rather more precarious. Photographs of the campaign capture hair-raising scenes of people working high above the ground on ladders and rudimentary scaffolds propped against the sarsens, or even standing directly on top of the lintels.

One of the people who was present during these works has been involved in the 2021 conservation, too. Richard Woodman-Bailey is the son of Aubrey Bailey, the previous projectโ€™s chief architect. Although only a young child at the time of the works, he accompanied his father to site and (in another ringing endorsement of safety practices of the time) before one of the sarsens was slotted back into place he was able to lean beneath the huge stone and slip a 1958 halfpenny into its socket. To mark the latest conservation initiative, English Heritage and the Royal Mint arranged for Richard (now 71) to strike a new commemorative silver ยฃ2, and to place it in the lime mortar being added to one of the lintels, where it will remain as an enduring part of the Stonehenge story.

Further information
For more details of the conservation work, and to hear an interview with Richard Woodman-Bailey about the 1960s restoration at Stonehenge, visit www.english-heritage.org.uk/visit/places/stonehenge/history-and-stories/history/conservation/?utm_source=Lintels.

To find out more about Stonehenge and how to visit the site, see www.english-heritage.org.uk/visit/places/stonehenge/history-and-stories.