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More secrets of Silbury Hill revealed in the book of the 2007-2008 excavations

The monograph telling the full story of the archaeological evidence discovered during multi-million pound Silbury Hill Conservation Project in 2007-8 is published by English Heritage today (December 28) - Silbury Hill: the largest prehistoric mound in Europe.

The book is the result of years of scientific and analytical work by 50 specialists from 20 organisations and universities.  The work was led by archaeologist Dr Jim Leary (then working for English Heritage, now a lecturer at Reading University) who has edited this monograph with David Field and Gill Campbell.

Opening the Hill for conservation, allowed archaeologists unprecedented access to its interior – and produced a great deal of new evidence.

“The post excavation analysis was vast.” says Dr Leary, “It was a major programme of scientific work and it took a lot of organising!”

Silbury Hill, the largest man-made mound in Europe, is a key part of the Avebury and Stonehenge World Heritage Site.  The huge earthen, grass-covered mound appears suddenly on your right as you drive from Marlborough westwards along the A4.


In May 2000 a ten metre deep hole appeared at the summit of the mound – as can be seen in the aerial photograph at left. This was caused by the collapse of tunnels dug into the mound in 1776 when Colonel Edward Drax became the first person to try to find out whether Silbury Hill was simply a giant burial mound.

It was then discovered that other, later exploratory tunnels driven into the mound by archaeologists were also collapsing – notably the one created during the excavations between 1968 and 1970 sponsored by the BBC and extensively televised. It was this tunnel that was then re-opened to give access for engineers to secure the collapsed tunnels and stabilise the mound - and for archaeologists to explore inside the mound.

Although there had been a great debate about what to do with the mound once it was found to be so unstable, if English Heritage had not stepped in and set a major conservation project in motion, Silbury Hill might well have suffered a catastrophic collapse.


Dr Jim LearyDr Jim LearyAs Dr Leary told Marlborough News Online, the major detailed findings in the new book using material discovered during the conservation work concern dating: “We now have a very good idea of its date, and of the length of time it might have taken to build.”

“The new dating evidence places the start of construction in the second half of the twenty-fifth century BC, with the final stages of Silbury finished in the late twenty-fourth or early twenty-third centuries BC – estimating that it took between 55 and 155 years to build.”

When Marlborough News Online asked Dr Leary whether there is likely to be further archaeological excavation on Silbury Hill after the 2007-2008 works, he explained: “They were not designed to answer pressing research questions about the nature of the mound. That must wait for the future.”

“That said, we know so much more about the mound and the landscape – things that just a decade ago we knew nothing of.”
The monograph has chapters on every aspect of the conservation and archaeological finds and analysis. Chapter 9 will be of special interest to the Marlborough area’s local history enthusiasts.  It tells how the project has revealed more about the later history of Silbury Hill.

A geophysical survey has revealed that a Roman settlement grew up around the mound.  And there is evidence that in the Middle Ages the mound was remodelled and a structure, possibly a defensive palisade, was built on the summit in the tenth or eleventh centuries AD – perhaps in response to Viking raids.

Another chapter gives details of the engineering work that was carried out to stabilise Silbury Hill and preserve it for generations to come.

With the results of the Silbury project safely between hardcovers, Dr Leary looks to the future: “We are surely about to enter a new phase, where dating of events allows us to build up local and regional histories and assign social context on the basis of greater certainty.  For Neolithic archaeology the prospects are really exciting.”

It is probably a good thing this book or monograph is being published after Christmas and so has missed family present lists – it is priced at £100.

The Marlborough Mound

The Marlborough MoundThe Marlborough MoundRecently, Dr Leary and a group of colleagues have also published analysis of the work he led in 2010 that finally dated the Marlborough Mound as being a contemporary of Silbury Hill.  

The mound in the grounds of Marlborough College became overnight not ‘Merlin’s Mound’ or ‘Castle Mound’ but ‘Silbury’s Little Sister’.  It is a little over half the height of Silbury.

It could certainly no longer be thought of as just the base for Marlborough’s Norman castle.  Rather, the castle builders used the Neolithic mound as a conveniently high foundation for part of the castle’s structure, rather as Silbury was probably used in the Middle Ages as the base for a defensive palisade.

Although the theory that the Mound was prehistoric goes back to 1821 and its date was the subject of controversy thereafter, it was generally thought to have been created in the Middle Ages.

The age of the Marlborough Mound was fixed using carbon dating of fragments of charcoal and other organic material found in the soil cores that were taken by Dr Leary’s team through the full height of the mound.

Published in The Proceedings of the Prehistoric Society (the December 2013 issue), the analysis of the findings leads the authors to believe it is likely the mound was part of a bigger Neolithic site – just as Silbury was part of Avebury and the Marden Henge had its mound (which has now disappeared.)

Dr Leary told MNO: “There is very likely to have been a Neolithic enclosure of one sort or another nearby.”  This was probably to the south of the Marlborough mound. However, as that area was turned into a network of water meadows in the seventeenth century, traces from Neolithic times have been lost.

The authors also think that evidence found in the cores taken from the mound, may show that the site suffered two major floods in the distant past.  Floods which may put the River Kennet’s more recent flooding into perspective.

In the journal paper there are intriguing photos of some of the cores showing the various strata of materials within the mound. 

These cores show the mound was, like Silbury, constructed over a number of phases showing that for the builders the significance of the mounds was in the process of building rather than in the finished form.

Silbury Hill: the largest Prehistoric Mound in Europe edited by Jim Leary, David Field and Gill Campbell.  Published by English Heritage. RRP £100.

The Marlborough Mound, Wiltshire. A further Neolithic Monumental Mound by the River Kennet – by Jim Leary, Matthew Canti, David Field, Peter Fowler, Peter Marshall and Gill Campbell.  Proceedings of the Prehistoric Society 79, 2013, pp 137-163.  
[This paper can be bought to download from the Cambridge University Press website for £20.]

[May 2000 aerial photo of Silbury Hill courtesy English Heritage.]

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  • Silbury-Sunset---10-06-08-----07
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