Her head of upper school, Mr Thomas, is leaning over the lectern, trying to look casual. There’s a girl sitting behind him, a sixth former, with her ankles crossed. Her long hair is the colour of dark chocolate, and it falls in waves over her shoulders. Her eyes are a shade lighter, more like milk chocolate. And her skin is smooth and tanned. Katherine assumes she’s one of those girls. Beautiful and bitchy.

‘Quiet please!’ Mr Thomas calls out. Then he turns his shoulder and flings one arm towards the girl, like a talentless ballerina. ‘Some of you may already know Becca Fischer in year twelve,’ he says. ‘Becca only joined us for sixth form, but she’s already making quite an impact.’ He smiles at her, then returns his attention to his audience. ‘Becca’s come along today to talk to you all, so if everyone can give her a warm welcome …’ A smattering of claps reverberates around the room as the girl, Becca – and no, Katherine doesn’t know her; they don’t breathe the same air – uncrosses her ankles and pushes out of the chair.

‘Thank you for having me, year elevens,’ Becca calls out once she’s arrived at the lectern. She’s holding one wrist with her opposite hand, Katherine notices, tightly too, because her knuckles are turning white from the effort. ‘I am the school’s anti-bullying ambassador, and bullying is a subject I feel very passionate about.’ This wasn’t the speech Katherine was expecting; she tilts her head and stares more intently at the stage.

‘Victims of bullying are often picked for no other reason than being a bit different from their peers,’ Becca continues. A bit different like having a face half covered in eczema, Katherine thinks. She gives in to the urge, scratches her chin, then contorts her face and shoves her hands into her coat pocket when the itch grows exponentially. Becca is still talking, but it reduces to white noise as Katherine becomes transfixed by her hands. She watches Becca unfurl her fingers from her wrist and, with an almost imperceptible movement, scratch melodically at her palms.

Gradually the sound of scuffing feet and noses trying to breathe through winter colds breaks the spell. ‘So it’s easy to brush negative comments off as harmless banter,’ Becca says. ‘But they can really affect people’s mental health.’ She walks in front of the lectern and Katherine can see the whole of her now. Sixth formers don’t have to wear uniforms and Becca is dressed in sage green cargo pants and a black top. She’s slim, maybe a size eight, so one year older and three dress sizes smaller than Katherine. The top is sleeveless and reveals her tanned arms, which seem too exotic for a rainy day in January. She’s not wearing make-up, but her eyes still seem to have a smoky frame.

‘And, with immigrant parents, I have first-hand knowledge of that.’