When you think of the Scottish Highlands, images of mountains and deep, mysterious lochs typically comes to mind.

       But the beauty of the Highlands, loved by King Charles, and appreciated by tens of thousands of tourists every year, hold a dark secret - and we are not talking about the Loch Ness Monster.

       One of the many Scottish Highland islands was once dubbed the 'world's deadliest' and had to be closed to the public for nearly 50 years. Setting foot on the island would have meant a painful death to visitors.

       Located close to a bay near Gairlock and Ullapool, Gruinard Island is a small, oval-shaped island approximately two kilometres (1+1？4 miles) long by one kilometre (5？8 mi) wide. At its closest point to the mainland, it is about one kilometre (one-half nautical mile) offshore.

       But the beautiful island has a much darker history than its neighbours. It was once a key World War II test site, known as a sacrifice zone, which left it severely contaminated with a deadly virus for nearly five decades.

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       In 1942, scientists set off anthrax spore bombs as part of 'Operation Vegetarian', to test whether or not the bacteria could be weaponised in the fight against Germany.

       The operation saw the military purchase the remote island and ban locals from visiting. Sheep were then used as test subjects for the subsequent anthrax explosion, with all of the livestock ultimately becoming contaminated and dying.

       University of Leeds professor later Edward Spiers explained in the 2022 documentary 'The Mystery of Anthrax Island' what happened.

       "Eighty-odd sheep were tethered at various stages downwind of the likely explosion It isn't a great bang, but a draught of highly potent spores moving down on the wind and causing infection and death wherever it goes."

       Anthrax spores never ended up being used in weapons but it was too late. The damage to the island was done and in 1945, the Government took responsibility of the island and judged it to be 'too hazardous'.

       The research would remain a secret by the UK government until the 1980s when 'Operation Dark Harvest' demanded the island be decontaminated but it wasn't be until 1997 the full details came to light, when a declassified military film was released into the public domain.

       To try and decontaminate the island, a mixture of seawater and formaldehyde was used, while the worst affected soil was removed and incinerated.

       A flock of test sheep was placed on the island after the clean-up in 1987, and luckily they remained healthy, leading the government to declare the island anthrax-free and remove warning signs that had been deterring people from visiting in 1990.

       But in 2022, the whole island caught fire with eye-witnesses calling the scene 'apocalyptic' and like a 'hell fire' at the time.

       The island was mentioned by Dean Munro who travelled the area in the mid-16th century. He wrote that it was "full of woods" but is treeless today.

       However it has inspired around a dozen novels including The Anthrax Mutation by Alan Scott (1971), The Enemy by Desmond Bagley (1977) , The Fist of God by Frederick Forsyth (1994) and The IMpossible Dead by Ian Rankin (2011)

       An episode of the wartime TV series Foyle's War entitled "Bad Blood" involved biological testing – a reference to the Gruinard testing.

       And in 1970 a Hawaii Five O episode featured a scientist playedwho threatened to unleash a deadly virus on the island of Oahu and under interrogation, the scientist mentions Gruinard Island and how it will be uninhabitable for a century due to anthrax experiments.

       Two years ago YouTuber Dara Tah decided to stay overnight on Gruinard and remove some of the soil for anthrax testing.

       Tah and friend Matt James donned hazmat suits for the video to be on the safe side despite the island's now contamination-free status.

       The samples the pair took from the island came back anthrax-free. So if you want to visit the fascinating island of Gruinard you are now safe to do so.

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