I’m watching him from my perch by the brook. He’s surrounded by old friends, holding Minnie in his arms, and I haven’t seen his face lit up like that for …

I don’t know. Way too long.

I’m just wondering which kind of cocktail to move on to next, when Suze comes swooshing up to me in her dress –which, I have to admit, is almost more fabulous than mine. It’s dark purple with a train and she got it in Paris from Christian Dior and wouldn’t tell me how much it cost, which means it was a squillion.

‘Bex, I don’t know what to do about …’ She pauses, then mouths, ‘Elinor.’

‘What about her?’ I look nervously around to check Luke isn’t in earshot. Suze leans close and breathes in my ear, ‘She’s still here.’

I feel a bolt of shock. She’s here?

Elinor told me a million times that she wasn’t staying for the party. She said she was leaving half an hour before we arrived. I just assumed she had.

‘But where …’ I look wildly around.

‘It’s my fault.’ Suze’s face crumples. ‘I just couldn’t bear for her not to see any of it. Not after everything she’s done. I knew she couldn’t actually come to the party … so I said, would she like to hide in the Priest’s Passage and watch?’

Suze glances up meaningfully and I follow her gaze. There’s a tiny iron balcony at first-floor level, which I’ve never really noticed. But it’s empty.

‘I don’t understand,’ I say stupidly. ‘Where is she?’

‘Hidden behind a secret panel, looking out through a spyhole.’ Suze chews her lip anxiously. ‘She said she only wanted to see you and Luke arrive and know that everything had worked. She said she’d slip away after that. But I just got Tarkie to go and check her car – and it hasn’t left. She must still be there! She hasn’t had any food, she’s just standing in this tiny space … and I’m worried. What if she gets ill? I mean, how old is she?’

Oh God. This could all go horribly wrong.

I glance over at Luke – but he’s laughing at something and doesn’t even notice me. ‘Come on, let’s go.’

The stairs up to the Priest’s Passage are tiny and narrow and musty, and I clutch my precious Valentino dress to me. As Suze cautiously pushes open the old wooden door, it’s Elinor’s shoulders I see first – narrow and rigid. Her face is pressed right up to the panel in front of her and she looks like a statue. She hasn’t even heard us.

‘Elinor?’ I whisper, and she whips round, a fleeting look of panic on her pale face.

‘It’s fine! It’s me and Suze. We’ve brought you a snack.’ I offer her a plate of mini desserts from dinner, but she shrinks away.

‘I must go.’

‘No! You don’t have to. We just wanted to make sure you were all right.’

‘Luke doesn’t suspect I’m here?’

‘No. Not at all.’

There’s silence. Elinor resumes her watch and I glance at Suze, who gives me a ‘What do we do now?’ shrug.

‘Luke and Minnie seem very close,’ says Elinor, her eye pressed right up against the spyhole. ‘He has a natural manner with her.’

‘Um … yes.’

‘With your parents, too.’

I don’t reply. This is all too surreal. How did I get into this situation? How can I be standing in a tiny cramped hole with my rich-bitch mother-in-law, both of us hiding from the man who links us?

And how can I be feeling like I want to give her a great big, warm, proper family hug? Like I want to gather her in, away from this dark, distant hiding hole, into the light and warmth of the party? She’s never seemed so vulnerable and alone as she does right now. And it’s because of her that we’re all having the time of our lives.

‘It’s just wonderful down there.’ I put a hand out cautiously and squeeze her arm. ‘Everyone’s said it’s the best party they’ve ever been to.’

‘Luke has enjoyed it?’ She turns.

‘Oh my God, yes! He’s bowled over! Did you see his face?’

‘You’ve made his year!’ Suze nods enthusiastically. ‘He’s so touched. He’s been round the whole forest, looking at every detail. It’s so clever.’

Elinor says nothing, but I see the tiniest flicker of satisfaction in her eyes. And suddenly I can’t bear it. This is all wrong. I want Luke to know. I want everyone to know. There was a massive driving force behind tonight, and it was Luke’s mother.

‘Elinor, come down.’ The words spill out before I can stop them. ‘Come down and join the party.’ I hear Suze’s astonished gasp, but ignore it. ‘Come on. I’ll make things OK with Luke.’