The Salvator Mundi was described as "one of fewer than 20 known paintings by Leonardo" when it sold for a record €400m in 2017, only to disappear amid increasing doubts about its attribution to the Renaissance master.
Months after the Louvre Abu Dhabi suddenly cancelled its unveiling, the painting is now facing an apparent snub from the Louvre in Paris, which is understood to have scrapped plans to display it in its major Leonardo exhibition.
Jacques Franck, who has been a consultant to the Louvre on Leonardo restoration projects, said politicians at the highest levels and Louvre staff "know that the Salvator Mundi isn't a Leonardo".
He is among those who believe it was painted primarily by one of Leonardo's studio assistants, and has written to French president Emmanuel Macron warning him against inaugurating the Louvre's autumn Leonardo exhibition if the Salvator Mundi, a depiction of Christ as the "Saviour of the World", is included. He has told him that it would be "almost scandalous".
He added: "The Louvre is the dominant museum collector of Leonardo in the world. They have the Mona Lisa, Saint Anne, St John the Baptist, the authentic version of the Virgin of the Rocks, and plenty of drawings. It would be a shame to have a 'workshop Leonardo' next to the Mona Lisa. I wrote to Macron not to inaugurate the exhibition if it were to be so.
"A lot of politicians have told me, it must be stopped. Macron cannot compromise himself inaugurating an exhibition where not-a-real Leonardo would be next to the Mona Lisa, presented as a beautiful masterpiece... Unthinkable."
Mystery surrounds the painting's whereabouts.
London's National Gallery unveiled it in its Leonardo exhibition in 2011, where it received support from some of the world's foremost scholars, breaking auction records at Christie's in New York in 2017.
After weeks of speculation about the buyer, with reports suggesting it was Saudi Crown Prince Mohammed bin Salman, Christie's confirmed that the Abu Dhabi Department of Culture and Tourism "is acquiring" the painting. Its September unveiling at the Louvre Abu Dhabi was cancelled without explanation.
Questions have also been raised about the painting's extensive restoration.
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