Most people will be familiar with Clywedog dam as a peaceful tourism spot - however nearly 60 years it was briefly anything but.
The dam was built in the mid-1960s, a huge, four year project that cost the equivalent of more than £100 million in today's money.
But in March 1966, three years into the construction, a terrific explosion tore through the site nearly derailing the entire project and destroying the Blonden aerial cable.
A huge police investigation immediately swung into action. The Montgomeryshire Express reported a week after the bombing - “Police were on the dam site again today interviewing workers – it is now estimated more than 300 people have been questioned - some more than once.”
Enquiries were led from CID offices in Newtown but it was reported that every police force in Britain was participating in the investigation.
“There are many lines of enquiry to be pursued,” said Detective Inspector G.E Hickley as he spoke to the Montgomeryshire Express.
Raids were made in “Cardiganshire and south Wales” while search warrants were issued for other parts of Wales and over the border in England.
After intense investigations one organisation was thought to be the suspect for the bombing. One who had already bombed a site in Montgomeryshire three years earlier - Mudiad Amddiffyn Cymru.
Mudiad Amddiffyn Cymru (MAC), meaning the Movement for the Defence of Wales, was a Welsh nationalist group set up in response to the flooding of the Afon Tryweryn valley and the village of Capel Celyn to provide water for Liverpool.
Formed in the early 60s, they had been taking part in bombings since 1963 and were now under the leadership of John Barnard Jenkins.
Jenkins, then in his 30s, was a former non-commissioned officer in the British Army's Royal Army Medical Corps. He had already been part of a land-buying scheme intended to disrupt the planned creation of the Clywedog Reservoir.
He was part of a subcommittee that bought two acres of land at the centre of the valley and sublet parts to contributors, including Jenkins himself. But Parliament stepped in to scupper the group's attempts to derail the project.
"They simply changed the law,” said Jenkins.
“This was the final thing which convinced me that constitutionally speaking, you can't win against people who own all judicial eventualities."
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The first targeted bombing under his leadership was a water pipeline at Llanrhaeadr-ym-Mochnant.
From there the group targeted multiple sites that were "interests of the British State", including tax offices, water pipelines, government buildings and infrastructure.
However it is thought that Jenkins was not involved in the Clywedog attack and that it was instead fellow member David Pritchard and other unknown members of the MAC.
In 1967 a pipe carrying water from Lake Vyrnwy to Liverpool was blown up by the group before things came to head at the investiture of Prince Charles in Caernarfon in 1969.
The evening before the investiture, two members of MAC – Alwyn Jones and George Taylor – were killed when a bomb they had been placing near government offices exploded prematurely. It was, however, one of four planted by the group that day.
On the day of the investiture, one bomb in the local police constable's garden exploded as the 21 gun salute was fired.
Another was planted in an iron forge near the castle. It failed to detonated when intended, and lay undiscovered for several days before seriously injuring its discoverer, who was a 10-year-old boy.
The final bomb was placed on Llandudno Pier and was designed to stop the Royal Yacht Britannia from docking - but this too failed to explode.
Later that year Jenkins was arrested and was convicted of eight offences involving explosives and sentenced to ten years' imprisonment.
In an interview shown on the BBC, Jenkins said that the bombs were never planted or timed to hurt people but just to disrupt the ceremony.
He spent the final part of his life working as a social worker before passing away in December 2020 aged 87.
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