THE Elan Valley’s stunning dams, scenery and walks are internationally renowned, but the significant role played by the beauty spot in history is probably not so familiar to many.

The Elan Valley was chosen for secret testing of explosives used in the ingenious Barnes Wallis ‘bouncing bomb’ – the key weapon deployed in the Dambusters Raid on Germany during World War II – 80 years ago this week.

Over night on May 16-17, 1943, crews from 617 Squadron, led by wing commander Guy Gibson, took off in 19 Lancaster bombers from RAF Scampton, in Lincolnshire, each carrying the ‘bouncing bomb’, and dropped them in Nazi Germany’s Ruhr industrial heartland.

The mission, which left German factories and mines badly damaged, was later immortalised in the 1955 film, The Dam Busters. However, eight of the Dambuster crews did not return and 53 men were killed. Three more, who were presumed dead, spent the rest of the conflict in prisoner of war camps.

County Times:  The remnants of Nant y Gro Dam today. The dam is a popular spot with Elan Valley walkers The remnants of Nant y Gro Dam today. The dam is a popular spot with Elan Valley walkers (Image: None)

The foundations for the success of that night, however, had actually been laid nine months earlier, in Powys.

In July 1942, the prototype charge was proof-tested at the small Nant-y-Gro Dam in the Elan Valley, where 280lbs of high-explosive destroyed the central portion of the masonry dam. The experiment was a complete success.

The idea for the Dambusters raid originated in 1940, when aeronautical designer Dr Wallis, assistant chief designer for Armstrong Vickers, calculated the explosive power required to breach the Ruhr dams and discovered that no existing bomber could carry a large enough bomb.

However, he realised that smaller bombs accurately positioned at the foot of the dam could have the same effect. To make this possible, Dr Wallis designed the bouncing bomb that would skip across the water and hit the dam.

The evocative remains of the bombed Nant-y-Gro Dam can still be seen today and are protected as one of Cadw’s scheduled ancient monuments. Walkers can follow a footpath from the Caban Coch Dam, on the opposite side of the river from the Elan Valley Visitor Centre.

County Times:  The Elan Valley dams. Pic by Phill Blagg The Elan Valley dams. Pic by Phill Blagg

The Elan Valley was chosen to test the bouncing bomb explosives because it was already being used as a firing range by the military. Due to its remoteness, away from the prying eyes of any Nazi spies, the picturesque valley was deemed to be the ideal spot.

Michael Booth, Elan Valley attractions manager for Dwr Cymru Welsh Water, said local people were proud that the valley had played such an important role in the development of the bouncing bomb.

“Nant y Gro Dam was a fifth scale of the Ruhr dams which is why it was chosen to test the bouncing bomb explosives,” said Michael.

“It was an abandoned dam in a quiet, isolated spot which fitted all the requirements of the RAF and Barnes Wallis.

“They needed to work out how much explosive was required and at what depth to cause maximum damage. There were three parts – the explosives, the bouncing bomb and the aiming system – and they all needed to work perfectly.

“The bouncing element was to ensure that the explosives detonated underwater and close to the dam structure.

“Part of the rich heritage of the Elan Valley, Nant y Gro Dam played a crucial role in the nationally significant events of May 16-17, 1943, during World War II.

“There are quite a few protected wartime remnants, such as pillboxes, around the valley reservoirs. During the war, Birmingham Corporation employed 600 special constables to ensure that the water pipeline from the valley to Birmingham was protected.

County Times:  Caban Coch, the lowest of the damns in the Elan Valley. Picture by Mick Pleszkan Caban Coch, the lowest of the damns in the Elan Valley. Picture by Mick Pleszkan

“These constables were each presented with a medal which features the Foel Tower at Garreg Ddu Reservoir in the valley.”

The remnants of Nant-y-Gro Dam are the focus of a popular self-guided trail and guided tour in the valley. The Elan Valley Visitor Centre also has a video and photographs in its exhibition of the dam being blown up in preparation for the Dambusters Raid.

The Elan Valley is three miles outside Rhayader, on the southern edge of the Cambrian Mountains. It covers an area over 72 square miles and is designated as an International Dark Sky Park.

The area is famous for its spectacular chain of six dams – Craig Goch, Pen y Garreg, Garreg Ddu, Caban Coch, Claerwen and the unfinished Dol y Mynach – and Victorian architecture.