A 5,000-year-old mystery over whether Stonehenge was once a complete circle has finally been solved – because a hosepipe was too short.
Historians have long debated if the outer prehistoric stones were at one time completely round – but have failed to find any evidence.
But this year the puzzle has been answered – because a hosepipe used to water the area wasn't long enough.
Every summer stewards at the ancient monument water the site to keep the grass healthy and the earth well nourished. But this year the hosepipe was too short to reach the outer part of the circle – where no stones still stand.
The dried-out land revealed marks of parched grass which were spotted by an eagle-eyed volunteer who alerted experts. English Heritage now reckons the discovery has revealed the location of missing sarsen stones which would have once completed the Neolithic circle.
Susan Greaney, from English Heritage, said: "It's really significant, and it shows us just how much we still have to learn about Stonehenge. A lot of people assume we've excavated the entire site and everything we're ever going to know about the monument is known. But actually there's quite a lot we still don't know and there's quite a lot that can be discovered just through non-excavation methods.
"It's great that people who know the site really well and look at it every day were able to spot these parch marks and recognise them for what they were. We maintain the grass with watering when it's very dry in the summer, but our hosepipe doesn't reach to the other side of the stone circle. If we'd had a longer hosepipe we might not have been able to see them."
Staff only water the site in the driest weeks of summer, but the hosepipe doesn't reach to the south-west quadrant where there is a gap in the circle.
Worker Tim Daw spotted the parched patches on the ground – now thought to be 'stone holes'.
He said: "I was on the public path looking at the grass near the stones and thinking that we needed to find a longer hosepipe to get the parched patches to green up.
"There was a sudden light-bulb moment in my head, and I remembered that the marks were where archaeologists had looked without success for signs that there had been stone holes, and that parch marks can signify them.
"I called my colleague over and he saw them and realised their possible significance as well. Not being archaeologists we called in the professionals to evaluate them."