The boys’ fight rumbled on into the same room as her and then two things happened, one after the other. The first was that a small wooden block, hurled by Stanley, presumably at his brother, missed its target and hit her smack on the head. ‘Ow!’ she yelped as pain buzzed through her temple. ‘Be careful!’ And then her phone chirped with a text from Mack – Back in an hour – and as she looked at it, she noticed what date it was that day. It was the shove she needed. The sign.

I’m going, she thought. Right now. I’m out of here. He’ll be back soon. He can have them.

Everything happened very quickly after that. She couldn’t even remember some of the details; it was like coming up on a nightclub drug, fast and vivid, the rest of the world blurring about her. There was the writing of a note to Mack, although she had no idea now what gibberish she might have written. She had calmly taken the boys round to her neighbour, Brenda, asking if she could just keep an eye on them for half an hour or so, until Mack got home, while she popped out.

(Popped out, indeed. You look after them, because I can’t any more was more like it. I’ve given up, Brenda. I’ve thrown in the towel!)

And then she’d stuffed some clothes in a bag and she was in her car, heading for the motorway, like a dream where she was running away, where she was escaping, only it was real. She was doing it – it was happening this minute. She felt drunk on adrenalin, wild but strangely still at the same time, as if there was a silent scream in her head that nobody else could hear. Something had taken hold of her.

As she drove on, she expected sirens to pursue her at any moment, she expected other drivers to see her and sound their horns in alarm – She’s getting away! That woman there, that mother just walked out on her children, and now she’s getting away! – but nobody stopped her. Nobody took any notice of her. She was so used to being the very visible mother of twins, with people smiling and commenting on them wherever she went – ‘Double-trouble!’ – but all of a sudden it was just her. A pale, plump woman hurtling along the motorway while her life collapsed behind her.

‘Oh my God,’ she said aloud and then she was shouting and crying like a maniac, and had to pull over at the next services because she was shaking so much. What was happening to her? Was this what a nervous breakdown felt like? What was she doing?