Maurizio Seracini is what Da Vinci Code author Dan Brown calls an “art diagnostician”, which is “not a bad description for someone who probes paintings with state-of-the-art-technology, often to advise museums, dealers and collectors on their restoration. One question raised by Mr Seracini’s painstaking investigation is why Da Vinci wanted to include such a bloody scene in a nativity painting, and why he – or someone else – thought better of it. But another question, and the one that will fascinate the Dan Brown fans, is what Da Vinci was up to on the other side of the painting in the last area of the panel to be fully rendered by Mr Seracini’s technicians.