The enigma of Silbury Hill

Last updated on August 23rd, 2023 at 01:44 pm

Silbury Hill is so regular in shape, so obviously artificial; yet it is large enough to be a natural feature. It stands some 130 feet (39.6 metres) high with a circumference at its base of about 1,640 feet (500 metres) – and is Europe’s largest manmade prehistoric mound.

You will find Silbury in the midst of the so-called sacred landscape of Avebury, in Wiltshire, in a valley floor between the village with its stone circle and the long barrow at West Kennet.  The Romans built a road and village at the foot of the hill and in the early medieval period the top may have been flattened and used for defensive purposes.  Perhaps this might explain the name; bury (from Anglo-Saxon) often means a fortified place of some sort – though it can also signify a manor house. Brewer’s not always reliable Dictionary of Phrase and Fable mentions the intriguing suggestions that Silbury is a corruption of Solis-bury – mound of the sun; or that Sil means seat or throne. Whatever, Silbury Hill is a great deal older than its modern label.

There are references to Avebury villagers meeting on top of Silbury Hill on Palm Sundays in times past, where they ate fig cakes, or puddings (Palm Sunday is, or was, sometimes known as Fig Sunday in parts of England) and drank sugared water, the water gathered from Swallow Head spring nearby.  It used to be common for traditional gatherings to be held in traditional places; perhaps this was a centuries-old custom at Silbury Hill.  It has also been suggested that the top, which is about 100 feet (30 metres) across, has been used for cricket – though I’d hate to be fielding if anyone hit a six. These days, alas, there is no public access to Silbury Hill, but you can observe it easily from the footpath between Avebury and the West Kennet Long Barrow – and you can see it when driving along the A4 west of Marlborough.  There is a lay-by roughly opposite, from which you can walk to the long barrow – and there’s a great view of Silbury Hill from there.

The purpose of Silbury Hill is lost in the mists of time.  However, it was obviously a very special place and, I believe, unique. The society that planned the project, and set aside the considerable time and effort needed to execute it – and this must surely have been an enormous investment for them, in relation to essential activities such as feeding their population – clearly had very specific objectives in mind.  We just have no idea what they were.  So far as we know, no one is buried in it – though there’s a tradition – earnestly put to me by one local – that a King Sil is interred in or under the hill; depending on the version, Sil is sitting on horseback, wearing golden armour, or lying in a golden coffin. Others believe the hill contains treasure.  It has been further suggested that it was a giant sundial, with a pole set into its top as the gnomon, casting its shadow on the turf below. Possibly, Silbury Hill was used for some kind of religious or other ritual, where the conductors or compères stood far above the audience.

There’s a story (with variations) that Silbury Hill was created when local Avebury wizards managed to deter the Devil from interring the entire population of nearby Marlborough under an enormous pile of earth, persuading him instead to deposit it where is now, thus forming the feature.  In fact, experts believe it was constructed from around 2,400^BC – contemporary with some of the pyramids of ancient Egypt and a similar size to the smaller of them.  Opinion is divided as to whether it was completed within a hundred years of being started, or some three or four hundred years later.  But there is agreement that it was built in stages, beginning with a small mound of gravel and clay, topped with another mound of turf and soil, with underlying chalk being dug out round it and added over a period of time, forming a surrounding ditch which was then filled and extended as the mound grew. Archaeologists estimate that it took 4 million man hours to complete.  If so, using a team of 20 working a 7 hour day, 7 days a week, and excluding time off for the great feasts of Samhain, Beltane and other public holidays (Christmas and Thanksgiving not having been invented), I reckon they’d have cracked it in about 78 years.

Silbury Hill has been explored several times in an effort to unlock its mysteries.  In 1776, a Colonel Drax of Dorset engaged miners from the Mendips to excavate a vertical shaft from the summit, but nothing was found to explain Silbury’s purpose*.  In 1849, the Dean of Hereford, John Merewether, directed the excavation of a horizontal tunnel, which revealed nothing but decayed moss and turf.  These early digs may well have destroyed evidence that might be spotted today.  A third exploration conducted by Professor Richard Atkinson between 1968 and 1970 partly followed the 1849 tunnel and identified three phases of construction.  Because none of these excavations had been properly backfilled, in 2000 they started to collapse resulting in a 46-foot (14 metre) deep hole on the top of the hill. This eventually resulted in an extensive project to stabilise the structure and undertake further investigation, including seismic surveys.  Archaeologists have been able to study artefacts like flint and antler tools, and further analyse biological remains (eg pollen and insects), which has given a better understanding of construction and dates.

But we still don’t know why Silbury Hill was built.

* I am grateful to Brian Edwards for pointing out that this work was not financed by the Duke of Northumberland, and that the miners were from the Mendips, not Cornwall. For more detail on this see Brian Edwards’ article Silbury Hill: Edward Drax and the excavations of 1776 in Wiltshire Archaeological and Natural History Magazine.