But it appears there may be an even richer treasure trove that will never be seen by the public, after bosses admitted they had lost thousands of items, worth at least £1 million.

While some of the artefacts are thought to simply be sitting in storage units, with curators not knowing where they are, many more are feared lost forever or even stolen.
Some of the world renowned establishments that have admitted misplacing valuable artefacts, include the Natural History Museum, the Science Museum, the Imperial War Museum and the British Museum.

While many of the missing items may only be valuable in historical significance, the British Museum has admitted mislaying a Cartier diamond ring, which is estimated to be worth £750,000.

The ring, which was bequeathed to the museum by an anonymous donor, was not on display when it went missing in 2011.

It was finally registered as lost earlier this year and the cost has now been written off by the museum.

Other, slightly less valuable items that have disappeared from collections, include an old tin of talcum powder and an old-fashioned Hotpoint washing machine, from the Science Museum.

The National Museum of Scotland has admitted misplacing a rare piece of quartz, while an important black tie has disappeared from a collection belonging to the Imperial War Museum.

Figures obtained by Sky News, following a Freedom of Information request, found that almost 6,000 items had been lost, stolen, misplaced or were officially "unlocated".

While the majority of items are thought to be in storage somewhere, they have to be classified as "unallocated", if curators do not know exactly where they are.

Jonathan Newby, deputy director of The Science Museums group: "Any object that we can't locate is unfortunate but this does come down to the record-keeping of museums.

"In the past, record collections started with a card index hand-written, then transcribed into databases that are now not what you would expect from a modern system."

Only a tiny amount of a large museum's collection will be on display at any one time with a huge volume of material in storage.

According to the Science Museum in London, it only has room to display around five per cent of its 400,000 piece collection.

The theft of valuable items has also proved a growing issue with around £80,000 worth of objects being reported as stolen.

In 2015 museums and art galleries were warned of a "severe and imminent" threat from thieves targeting priceless artefacts.

The Art Council warned that it had received intelligence that a concerted threat was in the pipeline.

In a letter sent to all major institutions at the time, curators were warned to "ensure that collections are held in facilities offering the best available defence against any attack".

But William Brown, head of security for the The Arts Council said systems were in place to protect the country's priceless collections.

He said: "I liaise nationally and internationally with other security experts from around the world. Our systems are the envy of many."

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