I shrugged. ‘Of course. It’s inevitable, isn’t it? If we were still the same now as we were twenty years ago, that would be . . . weird. Life shapes us, doesn’t it?’

In good ways and bad, I thought, trying to work out where Jennifer was heading with this.

‘I mean it changes everything.’

‘I don’t know about that – I still feel like who I was back then. Just a bit more sceptical.’

‘I remember when Jakey was tiny, probably six months or something, and I was already just pregnant with Ethan. The three of us went to Cromer for a week, to be by the sea. And while we were there we went out on a boat trip along the coastline, just for an hour or so. I was holding Jakey in my arms, and I looked at Alistair and knew, with absolute certainty in that moment, that if the boat went down and there weren’t enough life jackets – and I could only save one of them – I would save Jake without even a second’s hesitation. Not even a second. I would watch my husband drown if it meant saving my baby. It was like a scientific fact, like gravity; you couldn’t argue with it or deny it. And before I knew what I was doing, I could hear myself telling him this – I just came straight out and said it, without really realising I was saying it. I felt awful. But it was true.’

She fell silent for a moment, the breeze coming off the sea ruffling her blonde hair.

I said, ‘That’s natural, I suppose. A mother’s instinct.’

‘Yes, but do you know what Alistair said? He said he was just thinking the same thing. That he would save Jakey if he could only save one of us. So we both recognised, in the same moment, that each would sacrifice the other if it meant saving the baby.’ She was smiling a little now, shaking her head. ‘At that moment, sitting on that boat and feeling a bit seasick in Cromer harbour, it felt that something changed between me and Alistair. Changed from it being about me and him, into something else. Like it was the end of one chapter in my life and the start of another.’

I didn’t know what to say in response. This weekend, since seeing the messages on Sean’s phone, I’d felt that a chapter in my life was about to end, too. Rolling grains of sand between my thumb and forefinger, I wondered if Jennifer would be the cause. Tall, beautiful Jennifer, who’d turned Sean’s head when we first met as teenagers. Tense, worried Jennifer, who’d given off an air of brittle unease since we arrived in France.

She asked, ‘Have you ever thought that too? About Sean?’