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.

The present hardly exists, after all-it becomes the past even as it happens. A tricky medium, time - and central to the concerns of fiction.

The past is our ultimate privacy; we pile it up, year by year, decade by decade, it stows itself away, with its perverse random recall system.

I can walk about London and see a society that seems an absolutely revolutionary change from the 1950s, that seems completely and utterly different, and then I can pick up on something where you suddenly see that it's not.

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'm not an historian and I'm not wanting to write about how I perceive the social change over the century as a historian, but as somebody who's walked through it and whose life has been dictated by it too, as all our lives are.

You learn a lot, writing fiction.