A UFO expert believes he's solved one of the biggest alien mysteries in UK history - and says one man holds the key to confirming his theory.
The "Calvine Incident" is infamous as a picture captured at the scene shows a triangular craft flying low over the ground, and the image, taken in 1990, is of surprisingly high quality.
Behind the 'alien' craft is a conventional aeroplane, adding credibility to the theory that it was a UFO encounter that was handled by the military, as the Daily Star reports.
But now investigator Simon Holland believes he's figured it all out, as he believes the image taken in Perthshire, Scotland, is a secret military craft on a test flight.
What do you think about Simon's theory? Let us know in the comments...
The first development came on Monday, March 6, when the Daily Record reported that the image from the Calvine Incident was taken by a young Glaswegian hotel porter called Kevin Russell.
His name had previously been undisclosed, and after it was shared, former BBC Horizons producer Simon spoke out about his theory, suggesting that British Aerospace was working on a new radar-proof defence system.
He believes that this project may have included a diamond-shaped ship which was escorted by privately-owned Harrier jets.
Speaking on his YouTube channel about the image, which was taken near the A9 close to Calvine while Russell was out for a walk between working at the Pitlochry Hydro Hotel, Holland said: "I was sent the Daily Record story and I think it's fair to say that there are a lot of people out there excited at this exciting development.
"The Kevin Russell mentioned in the story would have the best, first-hand account of what happened and he could help settle this enduring mystery.
"But I do have my own theory on what he photographed."
The negatives are widely accepted to have been sent to the Ministry of Defence but were later lost – but one image was held onto by a press officer at the RAF.
Holland said: "I think there is an acceptance by many that the photo is not a fake. There was, I believe, a mysterious aircraft in the sky that day.
"The MOD previously stated, no 'known' Harriers were flying in Perthshire on August 4, 1990. That turns out to be a massive clue to whose they were."
He continued: "I discovered that the only other British Harriers were privately owned by BAE Systems, the defence contractor. They used their Harriers as multi-roll defence test platforms, testing BAE advanced technology.
"I dug deeper and found that Marconi Advanced Materials, based inside BAE HQ at Warton, Lancashire, were probably working on an advanced 'stealth' skin material for the USAF."
Simon said he recently spoke to the developer of British Aerospace's Stealth programme in late-1980s Lancashire, Ron Evans.
He said: "Ron did not confirm any Calvine testing but has explained the use of secret metamaterials to hide aircraft from radar.
"I think there is enough evidence to suggest there was something going on and it would be very helpful if the MOD would just come out and tell us all about it."
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