From Ancient Cairns to the Birth of the Bouncing Bomb; Dylan Iorwerth Joins One of Cadw's Regional Inspectors in the Hills of Radnorshire to Discover One of the Latest Historic Monuments to Be Scheduled in Wales and One of the Most
Agaping hole in its wall and massive boulders of smashed-up concrete are the features that make it so special. Looking down at the remains, Cadw's Regional Inspector of Archaeology and Ancient Monuments for Mid and North-East Wales Will Davies explains why.
Nant y Gro is famous for the Dambusters' Raid, immortalised in film. It was here, in May and July 1942, that Barnes Wallis carried out two experiments that would lead to the invention of his bouncing bomb.
Less than a year later, a squadron of Lancaster bombers attacked three dams in the industrial heartland of Germany's Ruhr, denting the German war effort and ensuring Nant y Gro's place on the schedule of monuments.
That means Nant y Gro is a monument of national importance protected by law from any actions that might adversely affect it.
Even work to conserve it will need Cadw approval. In contrast to listing, scheduling protects earthworks, ruins and buildings that are no longer occupied or in use; bridges are an exception.
Next, Will is looking for prehistoric cairns, standing stones and stone circles noted in a survey by Clwyd-Powys Archaeological Trust - the four Welsh trusts draw up lists of possible sites for Cadw's inspectors to visit, some for scheduling.
These are the two poles of Cadw's scheduling work - from prehistory to evidence of 20th-century conflicts.
In between are 4,000 castles, abbeys, deserted farmsteads and more unusual sites.
"Scheduling is our most powerful tool," says Kate Roberts, one of Cadw's two senior scheduling inspectors.
"It's about identifying archaeological sites that are of national importance and giving them protection."
Back on the open mountain, Will Davies is using his GPS device - the archaeologist's sat nav - to find out exactly where the prehistoric remains should be.
Even in driving, horizontal rain, the global positioning system is accurate within metres. He spots two poorly defined mounds in the heather and coarse grass, unmarked on his survey report.
Soon the red-and-white surveying rods are in place on two small heaps of stones, the tape measure is out and he is certain that we have found two more prehistoric cairns.
"It's often extremely difficult to be certain about these very early sites," he explains. "But context helps."
And he picks out the outline of other cairns and a fallen standing stone.
"These might not seem spectacular in themselves, but they are important as components of an extensive and undisturbed ritual landscape including a stone circle, enclosures and several other burial cairns and standing stones. …