“Daniel.” I feel like a kettle coming to the boil. “You can’t start laying new stuff on me now. The divorce is done. We’ve thrashed everything out already.”

“Surely it’s more important to get it right?”

He sounds reproving, as though I’m suggesting we go for a shoddy, ill-prepared divorce. One with no workmanship in it. Botched together with a glue gun instead of hand-sewn.

“I’m happy with what we’ve agreed,” I say tightly, although “happy” is hardly the right word. “Happy” would have been not finding his draft love letters to another woman stuffed in his briefcase, where anyone searching for chewing gum might stumble on them.

Love letters. I mean, love letters! I still can’t believe he wrote love letters to another woman and not to his own wife. I can’t believe he wrote explicit sexual poetry, illustrated by cartoons. I was genuinely shocked. If he’d written those poems to me, maybe everything would have been different. Maybe I would have realized what a self-obsessed weirdo he was before we got married.

“Well.” He shrugs again. “Perhaps I have more of a long-term view. Maybe you’re too close.”

Too close? How can I be too close to my own divorce? Who is this rubber-faced, emotionally stunted idiot, and how did he get into my life? I’m breathing so fast with frustration, I feel like if I rose from my desk now, I could give Usain Bolt a run for his money.

And then it happens. I don’t exactly mean for it to happen. My wrist moves sharply and it’s done, and there are six little ink spots in a trail on his shirt and a bubble of happiness inside my chest.

“What was that?” Daniel looks down at his shirt and then up, his face aghast. “Is that ink? Did you just flick your pen at me?”

I glance at Noah to see if he witnessed his mother’s descent into infantile behavior. But he’s lost in the far more mature world of Captain Underpants.

“It slipped,” I say innocently.

“It slipped. Are you five years old?” His face crumples into a scowl and he dabs at his shirt, smearing one of the ink spots. “I could call my lawyer about this.”

“You could discuss parental responsibility, your favorite subject.”

“Funny.”

“It’s not.” My mood suddenly sobers. I’m tired of playing tit for tat. “It’s really not.” I look at our son, who is bent over his book, shaking with laughter at something. His shorts are rucked up, and on his knee is a face drawn in ballpoint pen with an arrow pointing to it and I AM A SUPERHERO printed in wobbly letters. How can Daniel bail out on him like this? He hasn’t seen him for a fortnight; he never calls to chat with him. It’s as if Noah is a hobby that he bought all the equipment for and reached an elementary level—but then decided he’s just not that into after all and maybe he should have gone for wall-climbing instead.

“It’s really not,” I repeat. “I think you should go.”

I don’t even look up as he departs. I draw his stupid pile of papers to me, flick through them, too angry to read a word, then open a document on my computer and type furiously:

D arrives at office, leaving N with me with no notice, contravening agreement. Unhelpful manner. Wishes to raise more points regarding divorce settlement. Refuses to discuss reasonably.

I unclip my memory stick from its place on a chain round my neck and save the updated file to it. My memory stick is my comfort blanket. The whole dossier is on there: the whole sorry Daniel story. I replace it round my neck, then speed-dial Barnaby, my lawyer.

“Barnaby, you won’t believe it,” I say as soon as his voicemail answers. “Daniel wants to revisit the settlement again. Can you call me back?”

Then I glance anxiously at Noah to see if he heard me. But he’s chortling over something in his book. I’ll have to hand him over to my PA; she’s helped me out with emergency child-care before.

“Come on.” I stand up and ruffle his hair. “Let’s find Elise.”

The thing about avoiding people at parties is, it’s quite easy if you’re hosting. You always have an excuse to move away from the conversation just as you see a forty-inch pink-striped shirt bearing down on you. (So sorry, I must greet the marketing manager of the Mandarin Oriental, back in a moment.…)

The party has been going for half an hour and I’ve managed to avoid the Gruffalo completely. It helps that he’s so massive and the atrium is so crowded. I’ve made it appear totally natural that every time he gets within three feet I’m striding away in the opposite direction, or out of the room completely, or, in desperation, into the Ladies’….