Trouble is, we don't know if Silbury was originally built flat topped or changed later.

I can't resist commenting about the crop circle images. They illustrate something that's been evident for several years. Ever since the expert circle makers announced they were giving up, "someone" with a tenth of their skill has been trying to fill the gap. Who? Well cui bono? It's quite a big industry.

The circles used to be things of wonder, now they look far more like vandalism. It's sad.