Stonehenge may have been erected to unite early British farming communities, research finds

The altar stone, which we now know is from Scotland, may have been a gift or marker of political alliance

Five thousand years after the first monument was created at Stonehenge, it continues to give up dramatic new secrets - such as the jaw-dropping" revelation earlier this year that its central stone had been transported more than 700km to Salisbury plain from the very north of Scotland.

While it had been known for more than a century that the huge sarsens for which Stonehenge is best known come from more than 12 miles (20km) away and its bluestones" originated in Wales, the discovery that the altar stone, which sits right at its heart, was Scottish caused an archaeological sensation, capturing headlines around the world.