In the bustle of the platform, Tamsin felt their fears start to shrink into silliness. The boy headed decisively for the help-point phone, only to find it was broken. As they discussed what to do, their convictions gave way to embarrassment. At last Tamsin said, quite firmly, that she thought they had both overreacted.

The boy laughed nervously. ‘Right. Bloody hell. Don’t know about you, but I could really do with a drink.’

‘I was meant to be meeting friends in Camberwell…’ She looked up at him. There was a charming, improbable smattering of freckles across the bridge of his very straight nose. ‘But yes, a drink would be lovely, yes.’

He held out his hand, smiling for the first time. ‘I’m Chris.’

On the escalator, Tamsin felt the elation she associated with playing truant, but there was something else, too: an intimacy thrown over them first by fear and now, increasingly, foolishness. Yet at the entrance to the station, they both paused and breathed in deeply, tasting concrete in the damp November air. The world was newly sweet.

Chris took her to Gordon’s Wine Bar on Villiers Street. ‘A real gem of a place,’ he said loudly, as they made their way down the little stone staircase. The bar had low-vaulted ceilings and red candles stuck into old wine bottles, each with a dusty ruff of stalactites. The clientele was mostly male and middle-aged; but there were also some groups of younger drinkers playing for sophistication, and a fair-haired couple with matching hiking boots and a Rough Guide. Tamsin was nervous about her fake ID – thus far, she’d done most of her underage drinking in Camden pubs – so Chris, already eighteen, went up to buy the drinks. As she waited, she gazed round at the framed newspaper clippings, the cobwebs (evidently encouraged), the line-up of bottles behind the bar.

Tamsin was indulging in an old, childish game of deciding which instrument each wine bottle would be – some were square-shouldered like violins, others sloped gently from the neck like double basses – when the fear she’d felt in the tube rose up again. What if, at this very moment, people were dying because she and Chris had been too – too what? too selfish? too shy? – to act?

‘How will we know what’s happened?’ she asked Chris, as he placed a little carafe of red and two glasses on the table in front of her.

Chris shrugged. He started to pour out their wine, still standing, not meeting her eyes.

‘It was definitely nothing.’ He sat down opposite her, tucking his long legs under the table with difficulty. Tamsin waited for him to settle, then lifted her wine glass and tipped her head to one side.

‘Cheers.’

The clink of their glasses registered as a punctuation mark. Somehow, it had been agreed that neither of them would mention the suitcase again.