“We always start off with the plan of writing alternative chapters, but [that] doesn’t always work out in practice. One of us might get stuck and take longer to work through a particular chapter, or she might want to keep going and complete the whole of that section.  Also, the chapter outline might well change as we write: characters do things we hadn't anticipated, resulting in the story changing or needing to be told in a different order. The important thing is to get the first draft finished! Editing too early can be fatal - you just end up going over and over the same ground.”