‘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.