Yes, it's me.

I think that in the moment of standing there at 6am under a clear sky with Silbury Hill arising in front of me out of a ring of mist, like the mythological primeval island arising out of the sea of Nun, to then see the rising sun begin to slowly follow the angle of the slope brought to my mind the ancient Egyptian ritual where the new sun king ascends the stepped pyramid to reach the throne of Isis on the top of it.

In that moment it may well have seemed to me that the whole place had been created just to express that sort of idea, and I would not have missed that moment of 'revelation' for anything because it is a very beautiful poetic idea, but as soon as you take an interest in Silbury Hill and start reading about the stages in its construction it is clear that, while it may well have been intended to symbolise a new axis mundi of the type expressed in the above symbolism, the angle of the slope cannot possibly have been a consideration at the beginning.

It's also very true as you say George that it's a phenomenon more suited to being watched on video. When you are standing there with a camera you are far more likely to think about how to line it up to get it to work and also to bother to stay there and watch it all the way through; it can take two hours if you are close enough to the hill, or longer! I once got up at 2.30am to photograph the summer solstice sun rising up the side but the only viewpoint was ridiculously close up and the slope that side has two deep undulations. I was there for three hours. I might still have the sequence but I think it was unusable because the sun became too bright and massive too early on. The winter solstice sunrise is do-able, although the slope is not entirely perfect.

However from a good distance away such as within the area of the palisades enclosures where Pete's position was for the parallel you calculated, or from the other palisades enclosure at the end of the line on the palisades map which followed the azimuth of summer solstice sunset towards Silbury Hill there are excellent views with good straight slopes of an event which lasts 20 minutes and is spectacular to watch. On camera the sun tends to grow in diameter relative to what is seen by eye, and more so as it rises higher. Watching the real event the correct parallel becomes more important.

I can easily imagine people sitting in those palisades enclosures with a spectacular sunroll behind them totally unaware of it, surrounded by light pollution from their campfires and thinking mainly of pork bellies, so yes; Silbury Hill was built with slopes close to the angle of repose in order to give lasting stability to its shape and this happens to be close to the angle of sunset. Your take on it is certainly a possible reality.

My take on it, considering the symbolism of round mounds in ancient civilisations generally, and considering the habit of builders and architects of these civilisations to exploit natural coincidences in order to relate buildings to their surroundings, and considering the crop mark which is part of the palisades map that runs towards Silbury Hill at the azimuth of summer solstice sunset, is that the architects perhaps did not miss that opportunity.

I know that you calculated the parallel just to demonstrate that it was possible not that it was necessarily meaningful, but architecture is almost always intended to be meaningful, and if the sun was in any way meant to be associated with Silbury Hill then its slopes may not have needed much modification to accommodate a few sunroll viewpoints.

I do know of course that that's partly speculation but it's reasonable speculation given that the sunroll viewpoints do exist and that a solar association with Silbury Hill is entirely possible.

I remember going every morning in May (2010 I think) to see when the light beams from the rising sun would start getting back into WKLB from the other side of the front blocking stone. It was around the time that Steve M. was looking for a sunroll to maybe land in the spring next to Silbaby.

The light beam got in to WKLB again on 12th May, and there was a clear enough sky to see it enter the South chamber on 15th May. I ended up watching your sunroll with a small group of people the same evening from Pete's tripod position in the palisades enclosure.

Silbury Hill was built a thousand years after West Kennet Long Barrow was closed up but I now know that that light beam enters the south chamber of WKLB for four days (at least) from 11th/12th to 15th/16th May and in late July around the time that the sun rises at 60 degrees from North. The July dates for the light beam reach up to the time of Lughnasadh.

There seem to have been records of local people celebrating Lughnasadh on top of Silbury Hill into the 18th century, along with horse racing and bull-baiting. Lugh is of course a sun god.

It is impossible to know for certain I grant you but I think it would be a mistake to dismiss the idea that any of these things may have possible significance.

The fact that I acknowledge this does not mean that I am obliged to confuse evidence with proof!