PAINTING kept in a church attic and thought to be a copy of a masterpiece by Caravaggio is an unfinished work by the artist, according to Italian experts.

The Crowning with Thorns, now on display at the church of San Bartolomeo della Certosa in Genoa, has been restored by art experts who say they detect Caravaggio’s “unmistakable style” in the figure of Christ.

The placing of a crown of thorns on Jesus’s head before his Crucifixion is the subject of two known paintings by Caravaggio — one held in a bank at Prato in Tuscany and the other at Vienna’s Kunsthistorisches Museum.

The Vienna version was painted for Marchese Vincenzo Giustiniani, Caravaggio’s patron, and the Prato version for Massimo Massimi, a wealthy financier in Giustiniani’s circle. The Genoa canvas, measuring 203cm x 166cm, had long been assumed to be a copy of the Prato painting, which it resembles.

Piero Donati, superintendent of fine arts in Liguria, said yesterday that it was in fact a third work dating from August 1605, when Caravaggio took refuge in Genoa after fleeing from Rome after one of his frequent brawls.

He told La Repubblica that the painting was unfinished and that its lower half had been “completed” by Genoese artists. But the figures of Christ and his two tormentors had been painted by “an exceptional artist” who could only be Caravaggio. The painting had been found in a “pretty terrible condition”. It was restored by Paola Bracco, the expert who restored Caravaggio’s The Beheading of John the Baptist in Malta — the only painting signed by the artist.

Professor Donati said: “We do not know for certain how this painting got to Genoa. Perhaps Caravaggio took it with him to Genoa when he fled from Rome, or perhaps he painted it in Genoa to pay his debts to the Doria family for taking him in.”

A Crowning with Thorns attributed to Caravaggio was recorded in the mid-18th century in a Genoese collection. San Bartolomeo della Certosa is thought to have acquired the painting when the 13th-century church was restored in the late-18th and early-19th centuries.

Marco Ciatti, head of paintings at the Opificio delle Pietre Dure in Florence, Italy’s foremost art restoration institute, said that he had compared the Genoa Crowning with that in Prato and the Genoa version was “not a copy”. Professor Donati’s theory has yet to be proved.