It is around 4,750 years old and has been knocked about so much that it was in danger of falling into itself until English Heritage undertook some conservation a couple of years ago. This was due to a vertical shaft being dug into it in 1776 and a horizontal one in the mid 1800s. Then Flinders Petrie had a go in the early 20th century. Silbury Hill was starting to turn into a Swiss cheese.
The EH work allowed some archaeological investigations to take place; so every cloud has its silver lining. Dr Jim Leary found that the earlier interpretation by RJC Atkinson, that SH had three phases of construction, was wrong by a factor of 20 or more.
The mound we see today is 40m high and covers an area of 2 ha. It is estimated that it would have taken 18 million work-hours to shift 248,000 cubic meters of chalk and earth.
In many cultures it is the process of construction that is important, not the final outcome. Also the location is important. The hills position is associated with water, being near the Swallowhead spring of the River Kennet.
One of the most startling discoveries during the survey of the surrounding land was a large Roman settlement, covering 24 football pitches. Many mounds have Roman burials in them and they may have seen this gigantic mound as sacred themselves.
Another amazing discovery is that of a letter written by Edward Drax, who oversaw the Cornish miners digging in 1776. It was found in 2010 in the British Library. He had found a cavity, 12m deep and 15cm wide and stated that "we have already followed it about 20 feet and we can plumb it above 12 feet more". Drax interpreted this cavity as "something now perished must have remained in this hole to keep it open". David Dawson, director of the Wiltshire Heritage Museum, said: "It tells us that in one of its earliest phases some kind of totem pole was erected on the mound then subsequently additions to build up the hill were piled around that timber".
SH attracts many people, to see one of the most remarkable monuments in Europe. But this can also be a problem. Two people abseiled down the cavity that opened up due to erosion, thus not only putting their lives at risk, and others that may have had to rescue them, but added to the destruction of the monuments by doing so.
Such a reckless act of vandalism shows us that we must protect our irreplaceable heritage at all times.