The choreography of what happened has stayed with me. A hand, a large hand, warm, was laid on my neck from behind – not violent, oddly intimate, almost genial, cupping itself to the curve where neck meets shoulder. I was startled, but immediately assumed that a friend from the office had been following me from the restaurant and had caught up. No stranger would do that. I stopped and turned. It was a stranger. A tall, pale man whose lined face added twenty years to his age, which I guessed was only a few years ahead of mine, mid to late twenties. His hair, straight and dark, hung lank to one side, on a spectrum between Hitler and nineties indie dropout. That’s all the detail I can give. I have often tried to recall more, but even that basic outline is woozy as often as it is clear, and I wonder if any of it is invention, the imagination trying to help, supplying information not found in the memory. I’ll say this: he looked both unwell and in more formidable physical shape than me. His companion was even less clear.

Our dance continued. I had stopped in the middle of the pavement, by a street corner. He circled me, coming a little too deep into my personal space, which caused me to take a step back – which was not really a step back the way I had come because I had turned when I stopped. Instead I took a step backwards onto the narrower, quieter side street, a huge step really, across a threshold, not only from one street to another but from one situation to another, a step into a new world. And the old-young man was between me and the way I had come. It was impressive, really, the way that he sheepdogged me into the place he wanted me – a skill, a real talent. Absurdly, I was still trying to figure out if I knew him.

Behind me, movement. A shadow separated from the railings that ran along the side of the pavement.

‘Got a cigarette, pal?’

‘I don’t,’ I said. ‘Smoke. I don’t smoke.’

‘Got a quid? I’ll buy my own.’

The air around me changed. My pleasant boozy buzz from the party shut off. The wider city disappeared – the millions living lives, happy and sad and indifferent, all gone, down to me, and him, and the third person, the one manoeuvring on my blind side. And the details around me: the paving slabs under my feet, wet and black, the black railings, the unlighted windows of the building behind those railings, the dirty glass skylight between railings and wall, the dark shapes of the parked cars, a dull shine on them from streetlights too far away. This whole scene, a radius of two or three metres, was my whole world, and it was empty of help.