>>>>
I wrote the original account of Jim Leary's lecture posted on Eternal Idol (under my real name of Alex Down) and, in subsequent comments, I suggested that Silbury Hill might be the Avebury community's equivalent of Stonehenge, which I believe to be a symbolic representation of the Neolithic view of their cosmos.
In subsequent comments that I submitted yesterday (as I type here, still awaiting moderation on EI) I went further to suggest that the apparent post down through the centre of the hill might be equivalent of Yggdrasil, the central Tree of Life in the Norse cosmology. (A tiered layer view of the cosmos seems to be the common model, with a central axis.) So I was interested to see that a maypole cropped up in the comments on the archive find. When I looked at the Maypole entry in Wikipedia, I found this: "Potential other meanings include symbolism relating to the Yggdrasil, a symbolic axis linking the underworld, the world of the living, the heavens and numerous other realms. Also likely related, reverence for sacred trees can be found in ... " All a bit speculative, I know, but an interesting connection.