With thanks to the Daily Mail whose article dated 10th March 2017 made me aware of this site. As the Daily Mail is known for the highest standards in journalism, there's no need for me to do any research for the history of this site. I will just copy the article, amend names and add my own photos.
Eerie pictures reveal the secret 19th century Cornish mining tunnel used to test explosives for Operation Orpheus nuclear research during the Cold War
The photographs were taken at Excelsior Tunnel in Callington, Cornwall, by a daring man.
He took his son to explore the hidden tunnels but admitted he was alarmed halfway through the visit when he realised no one knew where they were - and the historic tunnels could be at risk of collapsing after days of heavy rain.
Under the code name of Operation Orpheus, the 2,180-foot underground passage became a testing ground for the British military to trial the impact of nuclear tests.
While civilians and Cornish residents carried on as normal, beneath the ground weapon experts were trialing potentially dangerous explosives.
According to newspaper cuttings between 1959 and 1960, some 75 explosions were carried out.
But CornwallLive reported local people didn't seem phased - or aware - of what was happening.
Weapons were fired in 6ft diameter voids at depths of 100 to 300 feet though no nuclear material was reported to be involved.
Why the Cornish site was chosen has never been disclosed but a writer suggested it was selected due to its depth and the fact it had been abandoned for some time.
Previously secret files released from the National Archives showed scientists had conducted "extensive geological investigations" on mines across Cornwall and Devon.
The document read: 'They were therefore very familiar with these mines and had many of the facilities on tap for reworking them.'
The Cornwall site was one of a few chosen places selected by Britain and America to trial weapons during the long war.
At Greenside Mine 3,000lb charges were detonated while massive explosions were set off in a salt mine near Louisiana in the United States.
And it was the rumours about the mine's military past which first ignited photographer Bertie's interest.
This led the 45 year old to daringly visit the site this year - accompanied with his son and his camera.
Inside the mines, he took a series of shots showing the hidden tunnels which were once used by miners and then the military.
One image shows the nondescript entrance, built into the side of the ground, which is largely hidden from view.
But while they were exploring, he admitted he became panicked when he remembered the days of heavy rain - and that no one knew they were there.
But he said the trip was worthwhile as he finally discovered firsthand a place he had heard about for decades.
The tunnel was first dug out in around 1880 to connect to a nearby mine shaft to gain access to tin but this was abandoned half way in.
During the Cold War, the tunnel was chosen to become the first site to experiment with the detection of underground explosions under the name, Operation Orpheus to coincide with the United States' Operation Cowboy.
There is no evidence that nuclear weapons were detonated there but in 1959, the Atomic Weapons Research Establishment exploded small charges into the granite of the tunnel at 100-feet and 300-feet.
The tunnel has been abandoned ever since the tests ended in 1960 and moved to Cumbria.
With thanks to the Daily Mail - revealing Urbex locations since 1896.
For a more comprehensive history, without use of the words "eerie" or "daring", visit the SubBrit page.
Eerie pictures reveal the secret 19th century Cornish mining tunnel used to test explosives for Operation Orpheus nuclear research during the Cold War
- Excelsior Tunnel in Callington, Cornwall, was used by the British Military in the 1940-50s to test weapons
- It was the first site to detect underground explosives under the name Operation Orpheus
- Images from inside the tunnel are revealed for the first time after a daring photographer paid a trip inside
The photographs were taken at Excelsior Tunnel in Callington, Cornwall, by a daring man.
He took his son to explore the hidden tunnels but admitted he was alarmed halfway through the visit when he realised no one knew where they were - and the historic tunnels could be at risk of collapsing after days of heavy rain.
Under the code name of Operation Orpheus, the 2,180-foot underground passage became a testing ground for the British military to trial the impact of nuclear tests.
While civilians and Cornish residents carried on as normal, beneath the ground weapon experts were trialing potentially dangerous explosives.
According to newspaper cuttings between 1959 and 1960, some 75 explosions were carried out.
But CornwallLive reported local people didn't seem phased - or aware - of what was happening.
Weapons were fired in 6ft diameter voids at depths of 100 to 300 feet though no nuclear material was reported to be involved.
Why the Cornish site was chosen has never been disclosed but a writer suggested it was selected due to its depth and the fact it had been abandoned for some time.
Previously secret files released from the National Archives showed scientists had conducted "extensive geological investigations" on mines across Cornwall and Devon.
The document read: 'They were therefore very familiar with these mines and had many of the facilities on tap for reworking them.'
The Cornwall site was one of a few chosen places selected by Britain and America to trial weapons during the long war.
At Greenside Mine 3,000lb charges were detonated while massive explosions were set off in a salt mine near Louisiana in the United States.
And it was the rumours about the mine's military past which first ignited photographer Bertie's interest.
This led the 45 year old to daringly visit the site this year - accompanied with his son and his camera.
Inside the mines, he took a series of shots showing the hidden tunnels which were once used by miners and then the military.
One image shows the nondescript entrance, built into the side of the ground, which is largely hidden from view.
But while they were exploring, he admitted he became panicked when he remembered the days of heavy rain - and that no one knew they were there.
But he said the trip was worthwhile as he finally discovered firsthand a place he had heard about for decades.
The tunnel was first dug out in around 1880 to connect to a nearby mine shaft to gain access to tin but this was abandoned half way in.
During the Cold War, the tunnel was chosen to become the first site to experiment with the detection of underground explosions under the name, Operation Orpheus to coincide with the United States' Operation Cowboy.
There is no evidence that nuclear weapons were detonated there but in 1959, the Atomic Weapons Research Establishment exploded small charges into the granite of the tunnel at 100-feet and 300-feet.
The tunnel has been abandoned ever since the tests ended in 1960 and moved to Cumbria.
With thanks to the Daily Mail - revealing Urbex locations since 1896.
For a more comprehensive history, without use of the words "eerie" or "daring", visit the SubBrit page.
