Everywhere I look, there seems to be an article on how to ‘be your best self’. Now, with Andy firmly on best behaviour, I seem to have turned into the very worst version of myself: that of a grim-faced parole officer, unmoved by praise.

‘Yes, but you make the best omelettes,’ Andy murmurs, gazing at it reverentially as if he might kiss it. ‘I’ve always said that.’

No, actually, I want to remind him, you’re only saying it because you couldn’t keep your dick in your pants. He looks at me across the kitchen table. Izzy – who thankfully still has no idea that anything is wrong – is tucked up under a blanket on the sofa in the living room, with a cold. I get up from my chair to go through to her. I’m still finding it difficult to be in the same room as Andy.

‘What’s the secret?’ he asks, having followed me through.

‘The secret of what?’ I frown at him.

‘Of your omelettes!’

‘Do you really want to know?’

‘Yes, I do,’ he splutters, looking hurt.

‘He does want to know,’ Izzy says, peering at me in confusion, which makes me feel as if my heart is being crushed. ‘Why won’t you tell him? Are you cross with Daddy?’

‘Of course not,’ I say with a terse smile as I scuttle out of the room.

I hide upstairs for a while, wondering how on earth we are going to get through this. We are doing our best to manoeuvre around each other, somehow managing to do the normal things that couples do, like cook dinner and watch TV and, of course, all the usual stuff with Izzy. All week, we’ve talked plenty about Estelle – long after Izzy’s gone to bed, obviously – as I’ve tried to drag every detail out of him: whether she’s married (yes), has children (no) and how successful she is in her field (‘Fairly,’ he admitted, reluctantly, which clearly meant: extremely).

It’s the length of time it’s been happening that’s the toughest thing to handle. It means they were ‘carrying on’ (such an old-fashioned phrase!) throughout Christmas, when I’d thought everything was fine and normal with us. But now I realise he was probably thinking about her when he carved the turkey. She’d have been on his mind when he and Spencer played a tipsy game of Jenga together, and when he hugged Izzy and told her the Christmas card she’d made him was ‘the best one I’ve ever had’.

How could he do this to us?

Naturally, I have googled the shit out of this woman. As I’m hardly sleeping anyway I’ve taken the sensible option of sitting up half the night, staring at pictures of her speaking at conferences and sitting on panels of Terribly Important Doctors.