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Other analysts say the sarsen stones may have served as a giant solar calendar so that people knew the time of year.

Professor Darvill said: "The proposed calendar works in a very straightforward way. Each of the 30 stones in the sarsen circle represents a day within a month, itself divided into three weeks each of 10 days."

Five centuries later, Stonehenge as we know it was built using some of those existing bluestones, as well as more than 80 towering “sarsen” stones, the monument’s vertical pillars, and horizontal lintels, or capping stones.

Each sarsen stone needed at least 1,000 people to transport it over a distance of 15 miles.

The sarsen stones were pounded into shape by circular hammerstones, several examples of which were recently discovered and are on show in an exhibition vitrine.