Using 70 years of BBC history archive film, Professor Alice Roberts uncovers how the iconic ancient monument of Stonehenge has been interpreted, argued over and debated by some of Britain's leading historians and archaeologists. She reveals how new discoveries would discredit old theories, how astronomers and geologists became involved in the story and why, even after centuries of study, there's still no definitive answer to the mystery of Stonehenge.

• Alice Roberts