Professor Colin Richards, of the University of the Highlands and Islands Archaeology Institute, is co-author of a new paper proposing that a stone circle in Wales was the source of the first megaliths erected at the site of Stonehenge.

Previously, the Stones of Stonehenge research project confirmed the Wiltshire monument’s bluestones came from quarry sites in the Preseli Hills in Wales. This prompted the reinvestigation the nearby Waun Mawn stone circle to see whether it also shared links with Stonehenge.

The results, published in the journal Antiquity today, suggest the Welsh stone circle was partially dismantled in prehistory and moved 280km (175 miles) to Salisbury Plain, where it was rebuilt to form the first of Stonehenge’s five distinct phases.

The research is also the subject of a BBC2 television documentary, Stonehenge: The Lost Circle Revealed, tonight, Friday, at 9pm.

Only four megaliths remain at Waun Mawn stone circle, which lies close to quarries that, in the past ten years, were identified as the source of the Stonehenge bluestones.

Around 3000BC, the bluestones were the first to be erected at Stonehenge – centuries before the larger sarsen stones were the brought 24km (15 miles) to the monument. At this point, Stonehenge consisted of a 110-metre outer ditch, a bank and a circle of 56 – probably bluestone – megaliths.

Today, all that remains is a series of filled-in sockets, the so-called “Aubrey Holes”, many of which contain cremation burials. Strontium isotope analysis of the earliest burials indicates that some had lived far to the west of Salisbury Plain, consistent with Preseli and west Wales.

Excavation at two Preseli bluestone quarries revealed that the megaliths were extracted long before the first stage of Stonehenge. So what were these stones for? This was the question that saw focus shift to Waun Mawn – in particular, whether it was the remains of a monument constructed using quarried bluestone and which was then dismantled to build Stonehenge.

But finding the Waun Mawn stone circle was not easy.

As far back as 2010, the researchers suspected the remaining four stones were part of a circle. Geophysics, however, proved unproductive and the next five field seasons were spent investigating other sites without success.

In 2017, in a last throw of the dice, they carried out a trial excavation at Waun Mawn and found two empty socket-holes. Renewed geophysical and ground radar surveys failed to reveal anything other than that the ground was unsuitable for geophysics. It was clear that only digging would reveal the buried sockets.

So far, excavation has located the position of six of the missing Waun Mawn megaliths. Extrapolating from these, the complete circle likely numbered 30-50 stones. These were arranged more irregularly than at Stonehenge, although two were positioned as “gunsights” forming an entrance aligned on the midsummer solstice sunrise.

The stone circle had a diameter of 110m, not only making it the third largest stone circle in Britain but matching the diameter of the ditch enclosing Stonehenge’s primary phase.

Optically stimulated luminescence (OSL) dating, which measures the length of time since quartz was last exposed to sunlight, indicates the circle was constructed between 3600-3200BC and is therefore one of the earliest stone circles in the country.

The excavation also revealed a lack of activity after 3000BC, by which point construction had started at Stonehenge. This, together with the fact that its bluestones came from known Stonehenge quarries, led the research team to conclude that Waun Mawn was taken apart and its megaliths used for a new monument on Salisbury Plain. Some were probably incorporated into subsequent iterations of Stonehenge and a few of the Waun Mawn megaliths may still be present at the site. For instance, one of the remaining Stonehenge bluestones has an unusual cross-section which matches one of the Waun Mawn stone-sockets. Chippings in that socket are of the same rock type as the Stonehenge stone.

To the researchers, the findings confirm that the Preseli area of Wales was an important and densely settled place in Neolithic Britain, with a concentration of dolmens and large enclosures. Yet evidence of activity in the thousand years after 3000BC is almost non-existent.

“It’s as if they just vanished,” said Prof Parker Pearson. “Maybe most of the people migrated, taking their stones – their ancestral identities — with them.”

The movement of the monument eastward seems to have been part of a wider of pattern of migration. Isotopic analysis of people buried at Stonehenge when the bluestones are thought to have arrived, reveals that 15 per cent came from western Britain, possibly west Wales. If Stonehenge was part of a large population migration east, the reconstruction of a monument from their homeland — using stones brought from it — may have been an effort to venerate their ancestors, history, and heritage from back west.

Another long-distance mover is the Altar Stone, recently sourced to the Brecon Beacons in South Wales. Prof Parker Pearson wonders if it too may have been part of another Welsh monument.

“With an estimated 80 bluestones put up on Salisbury Plain at Stonehenge and nearby Bluestonehenge, my guess is that Waun Mawn was not the only stone circle that contributed to Stonehenge,” he said.

“Maybe there are more in Preseli waiting to be found. Who knows? Someone will be lucky enough to find them.”

Some 43 bluestones survive today at Stonehenge, though many of these remain buried.

The original Stonehenge? A dismantled stone circle in the Preseli Hills of west Wales by  Mike Parker Pearson, Josh Pollard, Colin Richards, Kate Welham, Timothy Kinnaird, Dave Shaw, Ellen Simmons, Adam Stanford, Richard Bevins, Rob Ixer, Clive Ruggles, Jim Rylatt and Kevan Edinborough, appears in the February 2021 edition of Antiquity (Volume 95 No 379).