My UK publishers Sceptre turned 30 this year, with a splendid celebration on the new Hodder & Stoughton rooftop overlooking the Thames at Blackfriars. To celebrate they asked some of their authors to write a short piece about time, and the creative process. This was mine….

When I turned 49 I thought big birthdays didn’t matter; by 49-and-a-half, I knew they did. I marked my 50th by walking the 500-mile camino pilgrimage across northern Spain.

The idea was to reach Santiago by my birthday, but after my right knee swelled like a plump grapefruit on day two I had to let go of that plan.

I had to let go of just about every plan.

I was carrying too much: two novels for God’s sake, coloured pencils, three extra kilos of nothing. Then one day I found myself on a track through one of the most ancient human sites in Europe. Even though millions of pilgrims had walked before me, I knew I would find something.

And there it was, beside an olive tree, a fist-sized stone with pink marbled veins, sharpened half a million years ago, now softened by time and rain. It fitted so easily into my hand. I imagined its pointed edge applied to scrape the sponge and sinew from an animal hide.

When I held it I knew I would make it to Santiago. And I did. Each day I continued for an extra hour or three beyond nightfall, limping alone on the November roads under the stars or in mountain mists. I wondered if I felt afraid, but when I thought about that stone and the person who last held it I knew I wasn’t afraid, either of time passing or the lonely road.

Writing to deadline is like that for me. I think I won’t make it, I falter and doubt, then strength appears as if by gift, and I do.