Having written, you know, a… few books, I don’t expect novels to take me by surprise. Novels are large creatures. They’re like big and badly coordinated houseguests, who turn up and live with you for months at a time, sometimes outstaying their welcome, so that when they finally leave, you’re happy to see the back of them, what with them keeping you up late, night after night, and leaving their plot threads in your sink. They also plan their visits months or even years in advance: at any point in the last decade, I could have told you, in order, what books I’d be writing this year, next year, and sometimes the year after that. They line up, take a number, and then go and sit in the waiting room, glaring at me, surrounded by their carrier bags full of reference books, clutching their lists of problems and demands.

Once in a while, they turn up without warning. That’s fine. In fact, suddenly accommodating the unexpected is one of the real pleasures of being a freelance writer. It happens all the time in comics (my other job). I know what regular work I’ve got, but I often get asked to write a guest issue or filler issue at short notice to save a deadline, and suddenly I’m plunging into something, say Green Lantern or the Justice League, that wasn’t in my head at all. However, an issue of a comic is an easier, smaller beast to find a spare room for.

On several occasions, I’ve been asked to write a book that, until I got the phone call, I’d had no thought of writing. Instead of contemplating a novel for months before getting to write it, stewing the ideas and ingredients in my head, I have to find my way into it without any time to psyche myself up first. You get fresh results that way. It happened with Fell Cargo (phone conversation precis: ‘Can you write a novel about pirates real quick?’). It also happened with Xenos, the first Eisenhorn novel. My Black Library editor mailed me a bunch of reference material for the (then) forthcoming Inquisitor RPG, believing the lovely art and images might be useful 40K inspiration for my work on the Gaunt’s Ghosts novels. I was so inspired, I asked if I could write an inquisitor novel and, within a week, I was. I just jumped right in, and worked out what the hell I was doing as I went along.

That was 2001. Sixteen years and seven inquisitor novels later…

So I knew novels could be unexpected. And I also knew that novels sometimes turn into something completely different during the actual writing. I even knew I was capable of rewriting a book from scratch in a matter of weeks (the notorious ‘backup’ failure of Honour Guard).

But actually by accident…?

Turns out that can happen too.