Ever since I was a child and first learnt about Leonardo da Vinci's designs for helicopters that it wouldn't be possible to build for another three centuries, I have been fascinated by scientific prophets. It is not just a matter of awe before genius. What really caught my imagination was the question of what it was like to be ahead of your time, to know something you couldn't share with the people around you, to have knowledge that they couldn't or wouldn't accept.