I gather from one of our little blogging community (for which many thanks) that this is what MPP says about the glacial theory in his new book:
"John thinks that bluestone erratics could have been dumped south of Bristol in the area around Glastonbury where perhaps some remain to be found, buried beneath the peat. Even if this hypothesis were correct, Neolithic people would have had to move the stones forty miles from Glastonbury, or anywhere else in the Severn Valley, to Stonehenge."
I'm sure that this is a quote taken out of context, and that there is much more in the way of detailed discussion and analysis in the book, but just for the record here are a few brief points:
1. I do indeed think that bluestone erratics could have been dumped south of Bristol, but I also think they could have been dumped south of the Mendips, across the Somerset Levels, in the Glastonbury area, or up against the chalk escarpment, or even on the western parts of Salisbury Plain. All of that would have been perfectly feasible from a glaciological point of view. I am not THAT keen on Glastonbury as the dumping ground for bluestones from the west -- although I admit to being rather taken by the romantic idea of these two great iconic locations being connected by bluestones! As readers of this blog will know, I have played around with various ideas which are sensible when we look at the field evidence of glaciation in the South-West. But as ever, we need more evidence on the ground......
2. Yes, wherever the stones were collected from, they would have been moved over a greater or lesser distance by the stone gatherers. I have never denied that -- and as readers of the blog will know, my current theory for bluestone transport is in the nature of a "hybrid hypothesis" involving glacier ice (initially) and human agency (subsequently).
3. The Severn Valley? MPP has got his geography a bit wrong here. I have never suggested that the bluestones might have come from the Severn Valley -- the Severn Valley carried material broadly southward along the eastern edge of the Welsh uplands, and the ice affecting the area might have incorporated north or mid-Wales erratics, but not erratics from west Wales.