The place didn't look the same but it felt the same; sensations clutched and transformed me. I stood outside some concrete and plate-glass tower-block, picked a handful of eucalyptus leaves from a branch, crushed them in my hand, smelt, and tears came to my eyes. Sixty-seven-year-old Claudia, on a pavement awash with packaged American matrons, crying not in grief but in wonder that nothing is ever lost, that everything can be retrieved, that a lifetime is not linear but instant. That, inside the head, everything happens at once.

In old age, you realise that while you're divided from your youth by decades, you can close your eyes and summon it at will. As a writer it puts one at a distinct advantage.

I'm now an agnostic but I grew up on the King James version, which I'm eternally grateful for.

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.

We make choices but are constantly foiled by happenstance.

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'm not a historian but I can get interested - obsessively interested - with any aspect of the past, whether it's palaeontology or archaeology or the very recent past.