I recently gave a talk about Stonehenge called "Stonehenge: Bluestones or Red Herrings?" in which I explain why I do not believe that the bluestones were dragged hundreds of miles from south Wales by people, nor even were the huge sarsens dragged a "mere" 20 miles from the Marlborough Downs.
As a geologist, I am sure they were simply transported by ice to the Wiltshire Plain, from where they were erected to form the monument. There is a lot of evidence to support this (scientific and historical - in fact there are some surprising and very telling historical documents), and a lot of support from scientists, but their views tend to get quashed by publicity-savvy archaeologists such as Mike Parker Pearson, who has ridden the wave of popularism with his theories of the stones being excavated from Welsh quarries. Nowadays most people now don't think to question the idea of people dragging stones all that way but accept it as proven fact. It's become an archaeological mantra, propagated down the decades.
Hopefully I may be able to persuade your audience to look more objectively and critically at the "facts" presented by Parker Pearson et al. and make their own minds up.
