Her face is wary. ‘What if there was something wrong with the baby’s father?’

‘He was on drugs too?’

Zoë shakes her head. ‘No. He got clean. Cleaner than me, anyhow. I mean something in his blood. His genes?’

‘Oh.’ I was revising genetic conditions last week. ‘Well, we can inherit illnesses or traits from either parent. But even the more serious conditions can be managed if we know early on, ideally from birth.’

She says nothing.

‘Is this what you’re worried about? Talk to me, Zoë.’

But I’ve lost her to her memories or her fears. She starts to claw at the bedding and when she lifts the sheet, her bed is saturated. Zoë looks at the clear liquid and begins to sob.

Looks like labour is on, despite our attempts to stop it. ‘It’s all right, Zoë. It’s only your waters breaking. I think things might be moving now. I’ll just go and get the midwife.’

She grabs my hand and holds on. ‘Don’t leave me on my own!’

The midwife will be cross if I don’t fetch her straight away. But for once, I don’t want to do the correct thing. I sit back down, gripping Zoë’s hand back and I push the call button. ‘I promise you, I’m not going anywhere.’

There are times over the next nineteen hours when I regret making that promise to Zoë, but mostly I am focused on her and her pain.

She needs somebody. It could be anybody. But today it happens to be me.

I get sworn at, and her fingers leave bruises on my arm. I reassure her she can do it, even when I have my doubts. I ask her every few hours whether she’s certain there’s no one I can call – a friend, a family member, her baby’s father.

She swears some more.

Sometimes, when the door to the labour suite opens, we hear carols and Christmas songs coming from patients’ TVs. The contrast between the sentimentality of ‘When a Child is Born’ and the messy reality of Zoë’s labour makes me feel uncharacteristically feminist. Women are much stronger than men.

In the downtimes between contractions, we walk up and down outside the delivery suite, and I honour my other promise – to answer every question honestly. She uses it against me for her own amusement, as though we’re playing a one-sided spin the bottle.

‘How many people have you had sex with?’

‘Two.’

‘Wow. How many times a week do you do it with your girlfriend now?’

‘Once.’ This is not strictly true, not since Kerry found out about my exam screw-up, but I justify it by telling myself I am averaging it out over our three-and-a-bit years together.

‘Is she the love of your life?’

‘Yes.’

‘Are you the love of hers?’

I hesitate. ‘You’d have to ask her that question.’

Zoë nods. ‘Is she a doctor too?’