Dominica and Helga head off in the direction of the buoy, which is easily swimmable in the summer, but there’s a pull in the water, the tide going out, and it looks miles away. When Tor starts lagging behind, Helga comes to the same conclusion.

‘Let’s head that way,’ Helga says, nodding to the wooden groyne. As always, Tor is grateful to be in such a safe pair of hands. She knows it’ll be a relatively short swim. They only stay in a minute per degree of temperature, which Helga says is around eight today.

‘Oh, God, this is good. I can’t tell you how glad I am that Christmas is over,’ she says to Dominica. She means it.

‘I forgot to ask the other day. How was your family Zoom?’ Dominica asks.

‘Awful.’

‘Why?’

‘Because my sister, Alice, made such a big thing of it. She was even in heels. Who wears heels on Christmas Day?’

There’s a thrill to bitching about Alice tinged with a familiar guilt. They’ve been brought up to believe that their twin bond is sacred, but, often, it feels like that’s just a slogan. They might have shared a womb once, but that’s where the similarity ends.

‘We had to do this synchronised present opening. God, it was awful.’

In typical Alice style, she’d sent face cream and one glance at the back of the box had assured Tor that it was definitely not vegan. She remembers how Alice had told her to use it sparingly, as ‘the expensive stuff’ went such a long way. She told Tor to have a go at the wrinkle between her brow.

She does an impression of Alice peering at the screen, pointing out the Botoxed place on her own face that she finds objectionable on Tor’s, and Helga and Dominica laugh.

‘She’s so rude. And she doesn’t even realise it. I mean, we’re chalk and cheese. We always have been. But she always makes out that my appearance somehow reflects badly on her. It’s always about her.’ It’s not until she lets this out that she realises how much she needed to purge this resentment.

‘My sister was the same,’ Helga says.

‘Really?’ Tor asks.

‘Oh, she was a nightmare. She always looked down on me, even though I was the one winning sailing trophies. Didn’t matter a bit to her. She never acknowledged my success.’

‘I didn’t know you had a sister.’ Dominica sounds curious.

‘She died in a skiing accident when she was forty,’ Helga says. ‘My niece was only young. Mette. We’ve become close, but it would never have happened if my sister had lived because she was such a control freak. It didn’t help that she was married to an awful man. And I mean awful. I couldn’t stand the sight of him.’

‘I can’t stand my brother-in-law either,’ Tor says. It’s good to admit this out loud.

‘Oh. I love hearing about another arsehole,’ Helga says, flipping onto her back and nodding for Tor to proceed.