Unfortunately, an email dated 11 May last year has now surfaced in which the pair [of art historians who made the discovery] appear to be requesting electronic copies of the works. Neither are there any official records of them having viewed the works in person, according to Francesca Rossi, the official in charge of access to the castle's art and antiquities. She told Corriere della Sera newspaper: "I've never seen them here. They've never had access to the collection, they studied the images exclusively from the computer disc."

Reports yesterday suggest the disc sent from Milan to Brescia contained over 1,700 jpeg images – at low resolution. And in a very Italian twist, authorities in Milan have also announced an internal inquiry to establish if unwarranted collusion and even corruption was involved.

Mr Bernardelli disputed the claims of the Milan officials. "We saw the collection various times, even if these were outside normal hours, accompanied by different people," he said.

Other art experts have taken issue with the pair's conclusions. One critic, Professor Philippe Daverio, said that identification of a Caravaggio's organic and ever-evolving work could not be made by looking for the presence of key "designs". "Design doesn't exist in the character of Caravaggio," he said. "And design wasn't needed in his painting. These sketches can't really be compared to anything."

Another critic, Francesca Cappelletti, who helped to establish that The Taking of Christ was painted by Caravaggio, was blunter: "To me, these pictures still seem like typical works of Peterzano." Another critic, Tomaso Montanari, said sarcastically the claim was akin to taking 100 drawings by Verrocchio (Leonardo da Vinci's master) and attributing them to the creator of the Mona Lisa.