So I know how many psychiatrists it takes to change a lightbulb (one. But the lightbulb’s got to want to change) and how to get four elephants into a mini (two in the front, and two in the back).

What I don’t know, good people, is how many characters I can reasonably cram in my novel.

Many have fallen already, in the thirteen months (not that I’m counting) since ‘Madder Hall’ first stuck its nose past the parapet of my notebook (‘Wheeling a stolen bicycle, an ordinary-looking girl with yellow hair…’)* As I sit at my desk (oh, all right, in bed), with a Pivotal Scene to be written today, I’m pondering whether or not to cull another.

Now someone (whose name I’ve forgotten) said something (I can’t quite remember) on Radio 4 once, while lightly discussing the Eleanor Catton book-beast that garnered this year’s Booker Prize. It went something like this: writing plots is like carrying suitcases, one in each hand. If you’ve constantly got to go back for a pesky third suitcase, then maybe your plot is too complex. (Do please shed some light on the source of this quote, if you know it.)

For me, this particular character feels like that pesky third suitcase. I keep on forgetting her. Leaving her under a bench on the platform. (She nearly got blown up once, by controlled explosion, for being a possible bomb.) She’s only half-packed, as I vaguely recall: there’s a dirty great lock on the strap that I can’t find the code for. More bothersome still, she’s the same shade and texture as one of my other cases. I can’t always tell them apart at a distance. (Insert pic, here, of the author scratching her chin.)

But she plays very nicely in tandem with somebody else (her young daughter), and killing her off may cause the fabric of Time Itself to be hopelessly torn apart (or else necessitate a largish chunk of rewriting, which is far worse, of course). So here I am straddling this chasm, my legs at unnatural angles (as modelled here by Leroy in Fame), while the Pros and Cons swirl in my head. Do I welcome The Killer Inside Me or hack off that lock with a buzz saw and see what she’s hiding?

* As the re-writes have piled up (like hands playing One Potato, Two Potato) it turns out the yellow-haired girl can’t even ride a bike anymore. Which just proves the truth of this Rose Tremain quote (from the Guardian’s Ten Rules for Writing Fiction): ‘Respect the way characters may change once they’ve got 50 pages of life in them.’