We walked towards the main road. That was the end of the experiment, then – there would be no mugging. But neither of us said anything to declare the episode closed.

‘It’s not even eleven,’ Pierce said. ‘That’s the trouble. We’re too early. It was later than this.’

In the book, I thought. It had been later than this in the book, the crime that you had invented. I just wanted him to acknowledge that.

‘We should try somewhere else,’ Pierce said. ‘No sense giving up now. How about those big housing estates south of the river? Elephant and Castle. They were always a byword for mugging when I was growing up. I would never have gone there at night.’

I grimaced, which Pierce saw, and he tutted at me. ‘Come on, you said you were up for an expedition. We’ve got to do this properly, give it a proper try.’

‘Round here is one thing, but going all that way …’ I began, heeding the siren call of the fridge.

‘It’ll be fine,’ Pierce said. ‘With two of us I’m sure there’ll be no real danger.’

‘Then why …’

‘Just the right amount of danger, then. Come on. I’ll call an Uber to my flat, we can have a quick beer while we wait.’

I sensed that I was being bought off. But Pierce got something out of the deal as well – he didn’t have to walk back alone.

EIGHT

Pierce’s flat was three minutes away. That was one of the sympathetic details in Night Traffic: that the attack had happened so close to where he lived, in a neighbourhood he thought he knew. Again, that pang of rage at the calculation that had gone into the deception. We walked back together. Pierce had already summoned an Uber driver, but he would be half an hour. It was peak time for cabs: the pubs and parties emptying out, people on the move – peak time for muggers, too, perhaps.

Three brown bottles of cold Czech lager reclined in Pierce’s fridge. It was, I suspected, the same beer that had been there the previous day, and I marvelled at people who could do that, who could keep beer in the fridge without touching it, without even thinking about it, for days.