A new portrait by Leonardo da Vinci may have been discovered. The small picture of a young woman in profile was previously believed to be a German work from the early 19th century and has changed hands in recent years for around £12,000. But a growing number of scholars agree the work is almost certainly by the Renaissance figurehead because it appears to have his fingerprint on it. Carbon dating and infrared analysis back up the theory. The work could be worth tens of millions of pounds...