It seems to me that everything that happens to us is a disconcerting mix of choice and contingency.

I have had to empty two family homes during the last few years - first, the house that had been my grandmothers since 1923, and then my own country home, which we had lived in for over twenty years.

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

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.

I have long been interested in landscape history, and when younger and more robust I used to do much tramping of the English landscape in search of ancient field systems, drove roads, indications of prehistoric settlement. Towns and cities, too, which always retain the ghost of their earlier incarnations beneath today's concrete and glass.

You have this comet trail of your own lived life, sparks from which arrive in the head all the time, whether you want them or not - life has been lived but it is still all going on, in the mind for better and for worse.

I believe that the experience of childhood is irretrievable. All that remains, for any of us, is a headful of brilliant frozen moments, already dangerously distorted by the wisdoms of maturity.