I read your post with great interest and will make a point of buying the book next time I am in Avebury. I do not post here often but do look at TMA a lot, it is has a wealth of information tucked away.

It is accepted that there is a 'watery' reason for Silbury, usually attributed to a 'goddess theory' but to me a straightforward reservior/engineering explanation makes a lot of sense. Just in the last decade there have been great fluctuations in water levels around Silbury, with the Winterbourne drying up completely and the Kennet falling low in the few hot summers we had. Followed by flooding in 2007 when Silbury was in danger of collapsing while the restoration work was being carried out.

Thank you, I for one have learnt a little more about another possible 'why' concerning Silbury. One that is rational and credits Neolithic people with as much, if not more, engineering expertise as modern people.