For curators of a blockbuster Leonardo da Vinci exhibition which is opening today, it's been a nerve-racking few days. A total of 140 works by the greatest artist — who perhaps also possessed the greatest mind — in history were being brought together to commemorate the 500th anniversary of his death in 1519. Da Vinci was the ultimate Renaissance man. By the time of his death, aged 67, he had become an expert in countless areas: drawing, painting, sculpture, architecture, science, music, mathematics, engineering, literature, anatomy, geology, astronomy, botany, palaeontology and cartography. And the centrepiece of the Louvre show in...