I’ve lived in cities all my life, but living in Edinburgh is a completely different experience from the hustle and busyness of London’s West End. I was in London for a few days on business so my free time was restricted to an hour or so in the evening, before a rushed dinner with my colleagues and a swift return to the hotel to prepare for the next day.

I’ve always relied on my camera to unwind when I’m in a strange city. A gentle relaxed walk, camera in hand, documenting the novelty of a new day in a new town. What I wanted was a wander through St James’s Park, enjoying the autumn colours as the trees gently signalled the coming of autumn. With twilight giving the parks a slightly uneasy, ambiguous feel, I decided instead to photograph the relentless energy of the West End.

Making my way to Trafalgar Square I photographed all the cliché shots – the lions, the National Gallery, the water fountains. The photos were … okay. Record shots. Nicely done, and with the approaching blue hour giving great light. But ultimately they were snapshots.

Making my way to the south side of Trafalgar Square and looking down Whitehall, a police van was making its way through the congestion. Blue lights flashing, sirens blaring. Of course drivers and pedestrians made way, allowing the vehicle free passage through the busy road. But no-one was particularly interested. In a large, heavily populated city, strangers are largely anonymous. Someone else’s emergency. Just one of thousands of emergencies that took place every day. And you couldn’t possibly pay heed to every one.

I often think about the incident this van was rushing to. Was this a big interruption for someone whose life continued normally the next day? Was it a life-changing moment for a whole group of friends and family?

The next day, of course, I was back in the corporate world and I gave it no more thought. Except, from time to time, when I look back at this photograph and wonder.