There is a poster on the London Underground that takes your breath away. It shows the huge head of a tiger staring straight into the face of a young boy. Their noses are nearly touching - and the gaze of the boy is equally intent. In the space between their eyes is an invitation. It reads: 'Come within a whisker of nature's most breathtaking predator.' But it is the message I like to ponder most; which of the two is 'nature's most breathtaking predator'?