And then, Veronica left. She and her parents retreated to Brighton for the rest of the summer. And when almost a month later they were about to return to school, Veronica phoned to say that her parents were moving to Oman and she was going to boarding school, and could Sarah please also say hi to Eliza.

That autumn term, Sarah was not in a two. Neither was anybody else. Somehow, without discussion, the old pairings had dissipated. A number of the girls in her year had met boys at summer camp or on holiday, or at an elder cousin’s evening in, and some were now the overt holders of boyfriends. Liaisons lasted a week, two. At a month they were relationship veterans. They figured out their lasting compatibility by writing their names and crossing out the letters that corresponded to the word LOVE on the backs of their homework diaries. Occasionally a particular bomber-jacketed boy would turn up with a few friends in the school car park, and then they would untie ponytails and borrow each other’s hairbrushes and lip gloss, before sauntering arms hooked down the path to meet them. And coolly flicking their hair. At somebody’s Bat Chayil that December, a boy with floppy brown locks and unfinished stubble asked Sarah to ‘pull’ him. And she did.

Nobody mentioned the drama and fascination they had felt just months earlier in the friendships of twelve-year-old girls. They still had friends, and best friends, and took time to make the distinction. But they were no longer practising for other things.

Veronica did not stay in touch. She might as well have moved to Oman with her parents for all the difference it made her being in Kent. Letters trailed off by Christmas.

Yet Sarah had thought of Veronica. She thought of her when she closed the door to a too-small toilet cubicle, when her mouth went dry in a lift, or when panic struck her on the tube. She thought of her when she saw a flash of blonde hair, or tanned flesh diving into a swimming pool. She thought of her when she saw her own naked reflection on the bathroom wall.

She thought of her now too, eyes firmly shut so as not to see how close the MRI machine was around her. Of course the pool house had been the trigger. Of course it was Veronica. Of course the impact was material. Before then, she and Eliza had laughingly hidden themselves in the linen chest at the end of their parents’ bed; and they had buttoned themselves into duvet covers, delighting in losing the opening. She and Eliza. Eliza.

Sarah’s breath stuck suddenly in her throat. She had spent so long pretending not to blame herself for Eliza’s accident that she hadn’t even let her mind reach the logical conclusion of that thought.

Who had caused the claustrophobia that called for a car instead of the tube?

Who had put Eliza on the road that day really?