I’m throwing a party. Well, Tim is organizing it, on my behalf. Nothing on the scale of Marilyn’s four years ago, which featured a Spice Girls fancy-dress theme, a vodka bar, and my sister bursting out of a birthday cake, like her namesake, singing Happy Birthday to Me. (It wasn’t even ironic.)

Now she rushes into my room, wielding tongs and a fistful of hair products. ‘That’s perfect on you,’ she says, surveying my dress, a fifties style in a red mermaid print, which Mum bought me from a shop in the Lanes. ‘A great fit. It even makes your boobs look as big as mine. Tim’s not going to know where to look.’

‘We’re mates. Not all men are obsessed with . . .’

‘Sex? For a doctor-to-be, you have a lot to learn about biology, dear sister.’

Marilyn yanks me into my chair by my hair and, without ceremony, begins to tong a section of it. I’ve been her model since I was a toddler and she backcombed my fuzzy baby hair so roughly half of it fell out. I had the last laugh: my hair is now chestnut-coloured, glossy, and possibly the one thing about me she envies.

‘He’s probably organized a Harry Potter read-in at the library,’ Marilyn says. Tim hasn’t invited her.

‘You’re just jealous.’

‘Yeah, clearly I’m missing out on the party of the century.’

It is my party of the century. Maybe the best one I’ll ever have. I’m not stupid. I know none of this would have happened if it hadn’t been for that night. Before that, I didn’t have enough friends in the sixth form to fill a Mini.

Tim isn’t as keen on making new friends, but if I’m on my own now, other kids ask to sit with me at lunch or in the common room. And after they’ve got the cringeworthy stuff about me kissing Joel out of the way, we move on to chatting about normal things, too: music, and travel, and why no one has been arrested yet for killing Jill Dando.

‘Ouch!’ The hot tong sizzles against my neck. ‘Watch out, Marilyn.’

‘Who is coming? Will Joel be guest of honour?’ she asks, in a sing-song voice.

‘I’ve no idea.’

I want him there, obviously. But Tim has been in charge of invitations and he’s not exactly Joel’s biggest fan. Which is why I haven’t told Tim how often I still check in on Joel. Nothing’s happening between us – I am so not Joel’s type – but I can’t bear to think of him and his dad rattling around that huge house now Lynette’s away filming a property programme in Spain.