Once Upon a Time All stories begin with 'Once upon a time'. And that's just what this story is all about: what happened, once upon a time. Once you were so small that, even standing on tiptoes, you could barely reach your mother's hand. Do you remember? Your own history might begin like this: 'Once upon a time there was a small boy' - or a small girl - 'and that small boy was me.' But before that you were a baby in a cradle. You won't remember that, but you know it's true. Your father and mother were also small once, and so was your grandfather, and your grandmother, a much longer time ago, but you know that too. After all, we say: 'They are old.' But they too had grandfathers and grandmothers, and they, too, could say: 'Once upon a time'. And so it goes on, further and further back. Behind every 'Once upon a time' there is always another. Have you ever tried standing between two mirrors? You should. You will see a great long line of shiny mirrors, each one smaller than the one before, stretching away into the distance, getting fainter and fainter, so that you never see the last. But even when you can't see them any more, the mirrors still go on. They are there, and you know it. And that's how it is with 'Once upon a time'. We can't see where it ends. Grandfather's grandfather's grandfather's grandfather ... it makes your head spin. But say it again, slowly, and in the end you'll be able to imagine it. Then add one more. That gets us quickly back into the past, and from there into the distant past. But you will never reach the beginning, because behind every beginning there's always another 'Once upon a time'. It's like a bottomless well. Does all this looking down make you dizzy? It does me. So let's light a scrap of paper, and drop it down into that well. It will fall slowly, deeper and deeper. And as it burns it will light up the sides of the well. Can you see it? It's going down and down. Now it's so far down it's like a tiny star in the dark depths. It's getting smaller and smaller ... and now it's gone. Our memory is like that burning scrap of paper. We use it to light up the past. First of all our own, and then we ask old people to tell us what they remember. After that we look for letters written by people who are already dead. And in this way we light our way back. There are buildings that are just for storing old scraps of paper that people once wrote on - they are called archives. In them you can find letters written hundreds of years ago. In an archive, I once found a letter which just said: 'Dear Mummy, Yesterday we ate some lovely truffles, love from William.' William was a little Italian prince who lived four hundred years ago. Truffles are a special sort of mushroom. But we only catch glimpses, because our light is now falling faster and faster: a thousand years ... five thousand years ... ten thousand years. Even in those days there were children who liked good things to eat. But they couldn't yet write letters. Twenty thousand ... fifty thousand ... and even then people said, as we do, 'Once upon a time'. Now our memory-light is getting very small ... and now it's gone. And yet we know that it goes on much further, to a time long, long ago, before there were any people and when our mountains didn't look as they do today. Some of them were bigger, but as the rain poured down it slowly turned them into hills. Others weren't there at all. They grew up gradually, out of the sea, over millions and millions of years..