We all need a past - that's where our sense of identity comes from.

The Photograph is concerned with the power that the past has to interfere with the present: the time bomb in the cupboard.

The idea that memory is linear is nonsense. What we have in our heads is a collection of frames. As to time itself-can it be linear when all these snatches of other presents exist at once in your mind? A very elusive and tricky concept, time.

I didn't want it to be a book that made pronouncements.

But who knows their own child? You know bits - certain predictable reactions, a handful of familiar qualities. The rest is impenetrable. And quite right too. You give birth to them. You do not design them.

I didn't think I had anything particular to say, but I thought I might have something to say to children.

Perhaps I shall not write my account of the Paleolithic at all, but make a film of it. A silent film at that, in which I shall show you first the great slumbering rocks of the Cambrian period, and move from those to the mountains of Wales...from Ordovician to Devonian, on the lush glowing Cotswolds, on to the white cliffs of Dover... An impressionistic, dreaming film, in which the folded rocks arise and flower and grow and become Salisbury Cathedral and York Minster.