When the Queen decided to dust off an old painting for an exhibition at Buckingham Palace, it was to lead to a discovery that would shake the art world.
She has unearthed not just one but two Old Masters by the Baroque painter Caravaggio, so rare that Sotheby's are unable to put a price on them.
There are fewer than 50 Caravaggios in existence, all in either national or private collections, and one hasn't come on to the open market in living memory.
When pressed, the closest comparison Sotheby's could make was a Reuben sold in 2002 for £49.5million, making the Queen's clearout potentially worth £100million.
'The paintings are simply breathtaking and the significance of their provenance cannot be overstated,' said Lucy Whitaker, curator of the Royal Collection, as they went on display at Buckingham Palace yesterday.
The works, The Calling of Saints Peter and Andrew, and Boy Peeling Fruit, painted between 1592 and 1604, were originally acquired by Charles 1, whose collection of Italian masters rivalled any European court of the period.
For several centuries, however, they languished in a storeroom at Hampton Court after experts dismissed them as relatively worthless imitations of the originals.
The smaller of the two, Boy Peeling Fruit, did see the light of day for a while when Prince Charles borrowed it for display at Highgrove.
Miss Whitaker continued: 'Six years ago the Queen's conservator began some investigative work on The Calling of the Saints and started to clean it.
'Under layers of dull varnish and dirt, he discovered something much more interesting than we had ever thought before. It was very, very exciting.
'We have since had experts from around the globe examine the work and it has now, formally, been attributed to Caravaggio.
'As a result of this we decided to look at Boy Peeling Fruit again, which has also now been pronounced as an original.'
The process of authentication is rigorous and has involved academics from the U.S. and Italy as well as the UK.
'Experts look at everything from the way it is painted - Caravaggio's brushstrokes are swift and accurate - through to the amount of paint used and marks on the canvas.
'Obviously it is exciting to discover the provenance of any painting, but Caravaggio died very young, at the age of just 32, and as a result there are very few original works of his in existence today,' said Miss Whitaker.
'He is an artist that people feel very deeply about. He was always very controversial, for example painting the saints with dirty feet. But he was also very humane.'
Both paintings are part of The Royal Collection, which is held by the Queen on behalf of the nation. Despite their enormous value, she is not allowed to sell them.
They are on show as part of the The Art of Italy in the Royal Collection exhibition at the Queen's Gallery, Buckingham Palace, until January 2008.
Surveyor of the Queen's Pictures, Desmond Shawe-Taylor, said the display made up an 'unsurpassable' collection of Renaissance and Baroque art, including works by Titian, Leonardo da Vinci, Raphael and Michelangelo.
'We knew we had an unimaginably great collection and unbelievably wonderful individual paintings - but I don't think anybody knew quite how good it was all together,' he said.
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