Author photo courtesy of Smart Photography.

What was the first idea in this book that you built from?

There were two ideas, actually, and at first I didn't anticipate them forming part of the same book. I had already written the prologue - the scene where five-year-old Jacob slips his hand from his mother's and is hit by a car. It was inspired by a real life hit-and-run in Oxford when I was a young police officer, although the similarities end there. Sometime later I saw a magazine article illustrated with a photograph of a name written in the sand. I pictured a woman living by the sea in a very isolated cottage, making a living by writing people's messages in the sand. Gradually the character built up in my head. I knew she was escaping tragedy, but I wasn't sure exactly what that tragedy was. Then I remembered the opening scene I'd written, and the two halves of the story came together.

How much did the book change from your original idea, if at all?

The basic story remained the same, but over the course of eight drafts it became darker and twistier!

Did you have writing a book with a big twist in mind when you set out, or did it come to you after you started?

There are a few twists and turns in I Let You Go which came later - perhaps on the fourth or fifth drafts - but the Big Twist (!) was there right from the start. I wanted to play with the reader a little, and to challenge some of the assumptions we all naturally make about people and situations.

You have to phrase things just so in order to pull off the big twist - did you find that an easy or difficult part of writing the book?

Yes, I found that aspect incredibly challenging. There's one paragraph in particular - the end of a chapter - where a single semi-colon makes a crucial difference. That level of detail is exhausting but very satisfying.

How much of a role did your experience on the police force play in the details?

I didn't really have to do any research for this particular book, because it was all familiar territory for me. When I'm reading crime fiction and thrillers I'm always impressed when the author writes authentic police characters. For me I'm less concerned about procedure being a hundred percent accurate - it is fiction, after all - but more sensitive to the realism of a situation. Police officers calling each other 'Detective', for example, is something I see a lot in British crime fiction, but never happens in real life!

Will we be seeing more of Kate and Ray?

I've got no plans at the moment to return to Ray and Kate, but never say never!

Would you like to write a novel that doesn't involve the police or detectives?

I would! In fact I tried to with my second book, I See You. I wrote the first quarter just from one point of view, without a police viewpoint at all, but it didn't work. I needed that alternative perspective, and I had new police characters jumping around in my head, demanding to be written, so I gave in'¦ There is a book I'm desperate to write which isn't a thriller or crime novel at all. Maybe one day'¦

What's it like having a book released in another country? Is it as exciting as the first time?

It is JUST as exciting! I've found the US launch a little more nerve-wracking, actually. When I Let You Go came out in the UK no one had heard of it (or me!) so there was no pressure at all. It was a Sunday Times top ten bestseller for twelve weeks, and has sold half a million copies here, so now I'm much more nervous about what you guys think of it in the States! I hope you enjoy it.

Thanks Liberty and Clare! Liberty