When they are sixteen Cate puts a picture of Patti Smith on her wall, a life-sized poster of the cover of Horses. She got it at the Corn Exchange in town. They go to Afflecks Palace and search the musty racks for jackets like Patti’s. Hannah actually carries the look better, as she has no breasts to speak of yet. All that summer, on Monday nights, they tell Hannah’s mum she is going to a sleepover at Cate’s, and they take the bus into town to the Ritz, where they jump up and down on the bouncy dance floor to the Pixies and Nirvana and R.E.M. Cate wears tutus and Doc Martens boots and striped tops with frayed edges. Hannah wears long patchwork skirts and Doc Martens. If she pushed it any further, her mum would have a heart attack. As it is, when she applies kohl pencil, her mum nearly has a fit.

They go to a small town to the west of Paris on their French exchange and come back speaking halfway decent French. They walk on Saturdays, arm in arm in Fletcher Moss Park, where they practice speaking French in loud voices. They test each other on past exam questions: Emma Bovary is a tragic heroine. Discuss.

How is Emma Bovary responsible for her own downfall? Or do the nature of provincial society and the people around her make her unhappiness inevitable?

Their English teacher that year is a dedicated, energetic woman who believes in social mobility, in empowering girls. She suggests that they both apply for Oxford and she puts in extra time in the evenings, tutoring them both for the exam. They enter a new era of competition, spurring each other on.

One Saturday morning Cate’s mother falls, crumpled over herself in the cereal aisle in Asda. She goes back into hospital and Cate stays on a camping cot in Hannah’s room. At night, when Hannah is asleep, Cate lies beneath the duvet and looks at Hannah, cocooned in her sleep, in her security, and feels horror, waiting for her in the dark.

She goes to see her mum in hospice the week before she dies. Her mum’s eyes are enormous. She seems to take up so little room on the bed. The room smells sharp and thick at the same time. “Oh,” her mother says, when Cate comes into the room. It sounds as if someone is pressing her stomach, letting out all the air. Cate walks slowly towards her. She thinks this is probably the last time she will see her mother. Part of her wants to laugh; she puts her hand to her mouth and presses it to stop the laugh from coming out.

“Here you are,” says her mother as she gathers Cate to her. “Here you are.”