If the "cap fits - Telegraph A story now attached to the late John Sparrow, Warden of All Souls, Oxford, told of him at Parson's Pleasure, the Cherwell bathing place where men could swim unclothed. When a punt full of young women went by, everyone grabbed a book or hat to shield his nakedness, apart from Sparrow, who hid his head in his hands. "I don't know about you," he said, "but most people recognise me by my face." Now scientists in America, as we report today, have found a way of recognising us by our knees. Each knobbly knee is as unique as a fingerprint, the theory goes. So as we wait for hours to board a snow-bound plane, at least the machine will have established the true identity of everyone as they line up, by scanning their kneecaps. We are not quite convinced. Remember the claims made for iris-recognition machines, which now lie unused as queues lengthen.