How do you turn an idea into a novel?

For the last five years or so I’ve started each new book the same way – with a Papier notebook with a design that somehow reflects the theme or plot of the book, and a customised working title and my name on the front. Here’s the notebook I chose for the book that would become The Guilty Couple.

The idea

The Guilty Couple started life with a single thought – ‘I want to write a heist novel.’

This is where I admit that I’ve never actually read a heist novel but I have watched a L...