Many of us find it less inconvenient to be on our own, without the responsibility of commitment.

The other day, I was walking across London’s Southbank at night with a friend – let’s call her Charlotte – when a chap sporting a scraggy beard, an eclectic long-johns-and-shorts combo and carrying a complicated configuration of bags across his back appeared at my elbow. He thrust a paper cup half-full of wine in my direction and asked, “Can you hold this for a sec?”

“Sure,” I said. He walked on a bit as he rolled a cigarette. I half-thought he might wander off without his vessel, but he did eventually come back for it, before thanking me and toddling off. Interaction over, I forgot all about the episode until the following day when a thought occurred to me: what if it hadn’t been a cup?