But Silbury?

The official line from Jim Leary and his colleagues is that it must have been inspired by "ritual".

The trouble is, this is pretty much what archaeologists always say when faced with an object they don't understand: it must have something to do with religion.

"This is a big ceremonial mound," Leary insists. "It's not a big clock, it wasn't built for a bit of a laugh, or to give people something to do."

He points to the fact that there is none of the usual random detritus and debris associated with ancient secular building projects - no discarded meat bones, no ash from fires, bits of pottery and so on.

"This suggests that the site was always treated with some reverence."

In addition, large, solid "sarsen" stones (boulders similar to those at Stonehenge) have been found embedded in the chalk; one theory is that these represent the souls of the dead.

Maybe the whole thing is a sort of "virtual mausoleum".

That's the current theory.

But there have been a whole host of rather more outlandish ideas concerning Silbury over the years.

A long-standing legend holds that the hill is the tomb of King Sil, a statue of whom (in gold) supposedly lurks in a secret chamber to this day.

This mistaken belief that, like the Pyramids, Silbury Hill is full of treasure led to a series of attempts to dig into the mound, beginning when a team of Cornish miners were recruited by the Duke of Northumberland in 1776 to dig vertically into the hill from its summit.

In the 19th century, more tunnels were dug in the quest to find a hidden chamber.

Then in 1968 a huge series of corridors and chambers were excavated as part of that BBC project, in what can only be described as an act of archaeological vandalism.

No treasure was ever found, but that did not stop the speculation.

In fact, a delightfully bonkers belief system has arisen in recent decades which attempts to link ancient sites like Silbury and the Pyramids in Egypt with alien visitations, and even structures on the surface of Mars.

More UFOs are "seen" round here than anywhere else in Europe.

Stir into this brew crop circles (also often found conveniently nearby), ley-lines and the whole paraphernalia of the New Age and it is clear why the Avebury region is the mecca of the spooky brigade.

And indeed the Druids. Druidism is the catch-all term for the pre-Christian belief systems of western Europe, including the British Isles.

With the advent of Christianity, the Druids more or less died out, but in the 18th and 19th centuries, during the Romantic period, there was something of a revival of interest in the ancient beliefs.

Today, paganism has never been more popular.

Hence Terry Dobney's presence on the site.

He is here in his official capacity as Keeper of the Stones and, indeed,

 Archdruid of Avebury.

He has official status as on- site religious adviser, and yet I cannot help notice the somewhat sarcastic asides from the professional-team working on the site as they mutter about "Terry's theories".