We’ve arranged that Elinor will come to the house at 7 p.m., and by ten to seven I’m swigging wine, trying to stay calm. I never knew being a peacemaker would be so nerve-racking. Does the Dalai Lama get this stressed out before he spreads peace throughout the world? Does he apply his lip gloss three times because he’s so flustered? (Not very likely, actually.)

At least Minnie went to bed without a fuss, and the older children are happily watching Wall-E. The intervention should be over by the time they have to go to bed. Or I suppose it should. How long does an intervention take?

Oh God, why did I ever decide to do this?

On the plus side, the Intervention Room (i.e. kitchen) looks brilliant. I’ve lit about twenty candles for a mellow, calming atmosphere, and I’ve got soft music playing and I’m wearing a green dress which is very soothing. At least, it would be soothing if it weren’t for the fact that it cost me $280 last week in Intermix and today I saw it marked down to $79.99! They could have warned me. They could have given me some secret sign. That assistant must have been laughing her head off as she wrapped it up.

Anyway. Never mind. Luke doesn’t need to know all of that. The point is, the room is ready and I’m ready and now all we need is for Elinor to arrive. I can’t pretend I’m not tense. And I can’t pretend the atmosphere isn’t tense. I keep glancing at Luke, wondering how he’ll react.

He’s sitting at the kitchen table, sipping a beer, and his face is resolutely turned away from me. As I look at him, I feel a kind of plunging inside. We aren’t right. We aren’t us. It’s not that we’ve rowed again, it’s almost worse. We’re not making proper eye contact, and neither of us has mentioned our talk this morning. The only time I’ve seen Luke smile today was earlier on, when he was on the phone with Gary, his colleague.

Gary is in New York right now but flying back to London tomorrow morning. They were talking about the Treasury meeting and Luke seemed all fired up. He kept dropping in ‘Number 10’ and ‘policy’ and I could tell his brain was whizzing with ideas. He kept laughing at things that Gary said, and he seemed in a better mood than he has been for days.

I really, really hate to say it … but I think the truth is that high finance suits him better than movie stars.

Dad is still out, which I’m a bit relieved about, because he’d only want to join in the intervention and start telling Elinor she’d be a nice-looking girl if she’d get a bit of meat on her bones. And I haven’t heard from Suze since I saw her this morning, except for one text asking me to pick up the children from their activity clubs. I know she came back again to the house earlier, because Mitchell told me. Apparently she was still with Alicia and still looking for Tarquin. She went around the house yelling, ‘Tarkie! Tarquin, where are you?’ and then she drove off again. That’s all he had to say about Suze. He then proceeded to give me a full report on all the security breaches he had identified that day (two, both consisting of the little boy next door throwing his Frisbee into our garden).

I think Mitchell will be glad to leave. He was so bored today, he mended our barbecue, which he showed me proudly. I didn’t even know it was broken, to be honest. In fact, I must tell Luke.

‘By the way, Mitchell mended the barbecue,’ I say, awkwardly breaking the silence.

‘I was going to do that,’ says Luke at once, his jaw tight. ‘You didn’t have to ask Mitchell.’

‘I didn’t ask Mitchell! I didn’t even know it was broken …’ I trail off, in slight despair. I’ve got to get him in a better mood before Elinor arrives.

‘Look, Luke …’ I bite my lip. ‘Are we OK?’

There’s a pause, then Luke raises his shoulders in a shrug. ‘What do you mean?’

‘I mean this!’ I say in frustration. ‘Not looking at each other! Being all prickly!’

‘Are you surprised?’ says Luke heatedly. ‘I’ve spent the day managing fall-out from Sage and Lois’s stunt. A job which might have been easier if I’d known all along that it was a fake.’

‘Shhh!’ I say, glancing at the open door. ‘Jeff might hear!’

‘Right at this moment, I couldn’t care less who hears,’ says Luke curtly.

He looks totally fed up, and I know a lot of it is my fault.

‘Luke, I feel really bad for you,’ I say, reaching a hand out to his. ‘And I’m so sorry. I should have told you about Sage and Lois when you asked. But please look at me.’

Luke takes another slug of beer and finally meets my eyes.

‘Becky, life is tricky enough without us having secrets from each other,’ he says. ‘We should be on the same side.’

‘I am on your side!’ I say fervently. ‘Of course I am. I just wasn’t thinking. I’ve been trying to be independent … trying to get my career going …’

‘I get that.’ He sighs. ‘And I don’t mean we can’t be our own people. If you have to spend time out here for your career, then that’s what you have to do and we’ll make it work.’ He gives me a strained smile. ‘I can’t pretend I look forward to life without you – but if it’s really your dream, I’m not going to stand in your way.’ He hesitates, spinning the beer bottle round in his fingers, then plants it firmly on the table. ‘But we have to be honest with each other. We have to, Becky. Honesty is the foundation of everything.’

‘I know,’ I gulp. ‘I know it is.’

Oh God, should I quickly tell him about Elinor coming here tonight? Explain everything? Give him my reasons, tell the whole story, try to make him understand …

But it’s too late. As I’m drawing breath, the doorbell rings shrilly and I feel a clutch of nerves at my stomach. She’s here. Help. She’s here.

‘I’ll go,’ I say breathlessly, and make for the door before Luke can move. ‘Jeff, I’ll go!’ I call as I hear his heavy tread coming from the TV room. ‘I know who it is!’

I gave Elinor the code for the gate earlier and told Mitchell to put Echo away for the night.

My heart is hammering as I swing open the heavy front door. And there she is. My mother-in-law. The first thing I see is the nervous look in her eye. The second thing I see is the dress. She’s in a dress. A wrap dress. Elinor Sherman is wearing a wrap dress?

I blink in astonishment. I’ve never seen Elinor in anything other than a suit, or perhaps a very structured evening gown. Where did she even get this? She must have gone out to buy it specially.

It’s not the greatest fit. She’s so skinny, it swathes her body a little too loosely. And I wouldn’t have chosen that brown and cream print for her. But the point is, she’s in it. She made the effort. It’s as if she’s taken off her armour.

Her hair is different, too. I can’t quite work out how, because Elinor’s hair has always been a mystery to me. It’s not so much hair as a helmet. (Sometimes I even wonder if it’s a wig.) But tonight it’s looser in some way. Softer.

‘You look great!’ I whisper, and squeeze her bony hand. ‘Well done! OK. Ready?’

As we walk towards the kitchen I feel sick with apprehension, but I force myself to keep going. I can do this. I need to do this. We can’t go the rest of our lives with Elinor an outcast.

And we’re in. I retrieve the heavy key from the drawer where I’ve been keeping them safe from Minnie and hastily lock the door. Then I turn to face Luke, breathing hard.

I don’t know what I was expecting … I don’t know what I was hoping …

OK, I do know what I was hoping. I was secretly hoping that Luke would look up, and his face would turn from shock to rueful understanding to wise acceptance, and he’d say something simple like, ‘Mother. It’s time for peace. I see that now.’ And we wouldn’t need the intervention at all.

But that’s not what happens. He stares at Elinor in shock, but his expression doesn’t change. Or if it does, it gets worse. As he turns to me, shock veers to icy fury. For the first time ever, his expression actually scares me.

‘You’re joking,’ he says, his voice colder than I’ve ever heard it. ‘You’re fucking joking.’

‘I’m not joking,’ I say, my voice trembling.

Luke gazes at me a moment more, then strides to the kitchen door, without even glancing at Elinor.

‘I’ve locked it,’ I call after him. ‘This is an intervention!’

‘A what?’ He wheels round, his hand on the door handle.

‘An intervention. We have a problem and we need to fix it and we’re not leaving this room till we do,’ I say more bravely than I feel.

For a while no one moves. Luke has fixed his eyes on mine and it’s as though we’re having a private, silent conversation. It’s as though I can hear his words: You didn’t. You didn’t.

And I’m replying: I did. I so did.

At last, Luke swings round to the fridge and pulls out a bottle of wine. He pours a glass and hands it to Elinor, saying abruptly, ‘What do you want?’

My heart sinks. He sounds like a sulky toddler.

‘She’s your mother,’ I say. ‘Don’t speak to her like that.’

‘She’s not my mother,’ says Luke harshly.

‘I’m not his mother,’ echoes Elinor, even more harshly, and I see the surprise flash through Luke’s eyes.

They’re so similar. I mean, that’s the irony. They look like they’ve come out of the same Russian-doll set, standing rigid, their chins tight and their eyes steely with determination.

‘I forfeited the right to be your mother many years ago,’ Elinor says, more quietly. ‘I know that, Luke. But I would like to be Minnie’s grandmother. And your … friend.’ She glances at me and I give her an encouraging nod.

I know how hard this must be for Elinor. It so doesn’t come naturally. But honestly, with her hair loosened, holding a glass of wine, using the word ‘friend’, she sounds almost normal. She takes a tentative step towards Luke, and I long for him to see her the way I do. But he’s prickling all over with suspicion. He doesn’t want to see.