LONDON: A major excavation at England’s prehistoric Stonehenge standing stones started on Monday as archaeologists try to work out exactly when and why the first boulders were placed at the site.

Experts are focusing on the Double Bluestone Circle, which is located inside the iconic giant pillars on Salisbury Plain in Wiltshire, west England. The circle, thought to date from around 2,550 BC, consists of stones which came from the Preseli Hills in west Wales — 250 kilometres away.

One of the academics leading the excavation, Professor Tim Darvill of Bournemouth University, said the question of why they had been brought so far had niggled academics and travellers for more than a thousand years.

His colleague, Professor Geoffrey Wainwright, president of the Society of Antiquaries, added: “The excavation will date the arrival of the bluestones following their 250-kilometre journey from Preseli to Salisbury Plain and contribute to our definition of the society which undertook such an ambitious project.

“We will be able to say not only why but when the first stone monument was built.” Some experts believe that Stonehenge may have been a neolithic pilgrimage site to which sick people travelled in search of healing.

The excavation, the first inside the stone circle since 1964, will last two weeks.—AFP