"What usually happens is that when I'm nearing the end of one novel a vague idea about what I want to do next begins to present itself to me in terms of theme. And I would say over about the next six to eight months, usually as I'm out power walking in the morning, or when I'm cooking at night, or when I'm driving in the car, the people who might embody those themes take on a sharper and sharper focus. And there comes this sort of critical mass moment when they actually start to do things in my head."