As far as her mother was concerned, Tamsin was a textbook teenager: surly and non-responsive at home, perpetually in trouble at school. She collected detentions, missed curfews, got a tattoo. At fourteen she spent a night in A&E with a stomach full of vodka and caffeine tablets. At fifteen she pierced her own bellybutton. ‘Hormones’ became Roz’s buzzword, mouthed unsubtly over Tamsin’s head to sympathetic friends. Secretly, she was a little frightened of her eldest daughter. Tamsin at sixteen was a good six inches taller than her mother and almost ethereally thin, with angular shoulders and no hips or breasts to speak of. Cropped halterneck tops exposed the bejewelled bellybutton, elongated by the tautness of her stomach and embellished, more often than not, with a purplish crust of infection.

On the rare occasions that her parents argued, Tamsin lay awake in bed, monitoring the muffled sounds coming up from the kitchen for any change in register that might signal the end. The end: expected and dreaded yet also, in a small, hard way, longed for. But the rapid cadences of blame and recrimination always rallentandoed into a truce, followed, a few minutes later, by her mother’s face at the bedroom door, flushed with guilt and tenderness.

‘Darling. All couples argue. There’s nothing to worry about, I promise. Your father and I love each other. And we love you. Love you love you love you.’

Roz perched her small frame on the edge of the bed. Her daughter’s large-lidded eyes – Bertrand’s eyes – were round and wide, a precious glimpse of the little girl who had long since morphed into this difficult, untouchable half-woman.

And so the silence continued, as if it might go on for ever. But later, when Tamsin looked back at that time, she would recall very clearly a sense of anticipation. A firework mutely blossoming, Concorde ripping noiselessly across the sky: those vacuum-packed, suspended seconds before the bang.

Three

Five fifteen on a Tuesday evening in late November: the crowded southbound Bakerloo line. Tamsin Jarvis, now seventeen, still very skinny, had a seat. Even better, she had the end seat. This meant she could lean right away from the woman on her left and press her hot cheek onto the pane of glass dividing the seats from the standing section. She had shrugged off her parka at Marylebone to reveal a faded black Nirvana T-shirt bearing the slogan ‘flower sniffin kitty pettin baby kissin corporate rock whore’. In her lap, a book of Beethoven piano sonatas, open at No. 21. Tamsin had been tracing the melody with a chewed-down fingernail, pleasantly conscious of the incongruity: a grungy-looking teenage girl absorbed in classical music, performing the indisputable miracle of turning black marks on the page into sounds in her head.