Monday

My publisher calls, sounding worried. “So,” she says. “I’ve read the new ending for the last book.”

“Oh yes?” I say. I have the phone clamped under my chin, because I’m using a plastic Quidditch stick to jam twelve hundred copies of Harry Potter and the Goblet of Fire and a collection of Weasley figurines down the waste-disposal.

“Yes,” says the publisher. “And I’m not sure I like it.”

I switch off the waste disposal. “Really?” I say. “You don’t like the way Harry and all his friends get decapitated with an enormous axe?” “Not so much,” says the publisher.

I put a hand to my hip. “Or the way Voldemort disintegrates the body parts into a fine magic dust, which he sprinkles across time and space, thus eradicating Harry Potter et al from existence for ever?”

“Again,” says my publisher, “no.” I frown. “But I thought that was what everybody wanted,” I say. “Not everybody,” says my publisher.

Tuesday

I spend much of the morning trapped in my attic, under a landslide of Ron and Hermione pencil cases, Death Eater playing cards and polystyrene imitations of the Tri-Wizard cup. I shout, but nobody can hear. I clear a space with the wing of a papier-mâché Hedwig, and start a small beacon fire with a selection of latex Harry masks.

Perhaps it is wrong to change the ending of Harry Potter and the Deathly Hallows. It’s just that when I planned it, I rather liked Harry Potter; now I’m not so sure.

With a sigh, I settle back and watch my hero’s face burn and dribble into puddles on the floor.

Eventually, somebody will see the flames and set me free.

Wednesday

To Leicester Square this evening, for the film premiere of Harry Potter and the Order of the Phoenix. I’ve developed this weird tic whenever I pick up a pen. I sort of stop concentrating and start assuming it is a wand. The actress who plays Hermione Granger hands me a fountain pen and asks me to sign her copy of The Chamber of Secrets. I do, but it’s a close thing. I very nearly flick ink in her face and scream “Avada Kedavra!”

I suppose there is always crucifixion, I muse, staring at the back of Daniel Radcliffe’s head. That could work. I should rather like to see Harry crucified. Radcliffe sees me staring and goes quite pale.

Thursday

Have been worrying, hugely, about Voldemort. I mean, it wasn’t really him who killed Harry’s parents, was it? It was me. It’s all my fault. The poor man. A decade spent banished in a magical nether region, unable to flourish truly in his own right.

Everywhere he goes, Harry Potter goes too. Thwarting him. Stealing his thunder. I sort of know how he feels.

Friday

“No,” says my publisher. “Absolutely not. It has been ten years. We have well over 12 million copies of Harry Potter and the Deathly Hallows ready to roll off the presses, just as soon as you come up with this bloody last chapter. It is definitely too late to decide that Voldemort has been the hero all along.” “Really?” I say.

Explore Books

• Book Extracts

• Book Reviews

• Books Group

• Audio Books

Times Recommends

• Superfreakonomics by Steven D Levitt and Stephen J Dubner
• The Times picks the 50 best paperbacks of 2009
• Vincent van Gogh’s letters show the soul of the artist