But not all critics agree on the paternity of the sketch which long adorned the wall of a former kitchen, with The New York Times shining a spotlight on the affair.

The villa in the hills of Settignano was sold by the Sernesi family at the end of last year without the drawing, a charcoal on plaster mural depicting a satyr or triton which was removed from the wall to be restored in 1979.

Over the years, the work has travelled the world, loaned to shows from Japan to Canada, and most recently to the Metropolitan in New York for the 2017 exhibition Michelangelo: Divine Draftsman and Designer.

Catalogue curator Carmen C. Bambach confirmed the attribution, describing it as “the only remaining evidence of Michelangelo’s abilities as a large-scale draughtsman”.

Rumours of the Florence auction have rekindled the attribution debate which had remained hitherto limited to the small circle of Michelangelo aficionados.

While Bambach, an authority in the field of Renaissance drawing, confirmed its authenticity, other experts are not as certain.

For Cecile Hollberg, director of the Accademia gallery that houses the David and who viewed the drawing for the Sernesis, “it is very interesting and now it is certainly necessary to carry out fresh investigations”.

Works of masters of Michelangelo’s calibre still in private hands are extremely rare and prices are eye watering when they come to market. For example, two years ago a Michelangelo sketch was auctioned at Christie’s in New York for 23 million euros.

Italian prices are considerably lower because of laws against exporting works of art, Milan and London gallery owner Carlo Orsi explained to the New York Times.

“Finding customers in Italy at these prices is virtually impossible,” he said.

The Sernesi family has not put a price on the work which was insured for $24 million when it flew to New York for the MET show.

“We think it is a work that desreves to be seen and appreciated,” Ilaria Sernesi, one of the owners, told the NYT.

As well as the association with the villa, the attribution of the drawing to Michelangelo is also based on the assessment of Hungarian art historian Charles de Tolnay, who says the Sistine master sketched it as a teenager.

Comparisons between the Sernesi drawing and a study by Michelangelo in the Ashmolean Museum in Oxford have prompted other experts to date the work to the first 20 years of the artist.

One of the attribution skeptics is Paul Joannides, emeritus art historian at Cambridge, who highlights its “scant quality”.

Also in the no camp is Francesco Caglioti, of the Normale University in Pisa. “If it was by Michelangelo, he wasn’t on great form that day,” said Caglioti.

The artist, he added, “was a severe judge of his own work” and in his old age destroyed several juvenile works.

“Perhaps he forgot about this one,” Caglioto told the NYT.

ANSA