How was the Stonehenge Altar Stone moved from Scotland?

I’ve had a keen interest in Stonehenge since I directed my first excavation there more than 40 years ago. A personal highlight was identifying a skeleton in London’s Natural History Museum, which archaeologists thought had been destroyed in the Blitz, and which turned out to be the remains of an Anglo-Saxon man beheaded beside the stone circle. Claims are made weekly, it seems, for some new insight into Stonehenge’s meaning, history or construction – and not all of them are mad. But I cannot remember an occasion when a single discovery changed the way I think about Stonehenge as much as the one announced this week. 

A Nature study has found that Stonehenge’s Altar Stone was quarried in the far north-east of Scotland. Which means – depending on the route – it was carried as far as 800 miles before it was finally laid in Salisbury plain.