Google maps are one thing but there's no substitute for pounding the beat and I spent quite a bit of time figuring out how to break into the back of the houses on Belgrave Place. Once I even for followed by a suspicious householder - I'd been hanging around staring at the exterior of his flat for too long.

In the middle section of the book Mirabelle breaks into not one, but two houses near Belgravia Books. I had fun scoping these out - checking which windows looked least secure and figuring out how to scale the mews houses to the rear to get her inside. A man came out at one point, 'What are you doing?' he questioned me. 'The thing is, I'm writing a book,' I started with a smile. He waved me off, his hand as wide as a tennis racket. 'Everyone is writing a book, my dear,' he said. Between you and I, it's his house that MIrabelle ends up breaking into.