In London you trip over other people's conversations from the moment you close your front door and step into the public domain. It's like the city was designed for it: waiting to pay at Tesco, anywhere on the tube, even walking home through the park, the one sure thing is that you're going to inadvertently wander in, through, and then out of the smoke and fog of someone else's conversation. It's a given. A certainty.

No reason either why it should n't be either; there's nine, possibly ten, maybe eleven, or even twelve, depending who you believe, million people squeezed in to London. So why should n't we be dipping in and out of a smog of small talk?

As I ploughed through Holland Park on my way home earlier this evening, I fleetingly drifted into range of a kind of Q&A going on between a family of three, and snagged a line that resonated instantly. The father was agog about a bird of prey they'd once seen. I don't  think it was recent - something in his tone suggested that - nevertheless it carried epic connotations. It had taken his breath. It had awed him.

I know all about that despite never seeing whatever he saw; something similar happened to me at the Barnes Wetland Centre one late winter's evening last year. I'd just followed a friend into the quiet gloom of  a bird hide. He turned towards the larger front window and I made for one of the smaller side panels. In front of me, perhaps no more than six or seven feet, sat an impassive sparrow hawk, tawny brown and steel-eyed, the lean face of death, the master of the urban skies. I felt like a veil had been pulled aside and I had been given a glimpse of another reality, where I was the intruder and the sparrow hawk was master.

I've had very few moments where nature has allowed me this snatched view of a master hunter's almost imperial disdain. Quite unforgettable. For me then and just as much for the anonymous father I overheard a few hours ago talking about his own moment of wonder.