Squaring off

I had a surreal moment this morning. I was cutting through Paternoster Square, which is usually a rat run for pedestrians. But as I turned into it, everyone was standing stock still, as if frozen.
I checked to see if they were looking at anything, but they were facing different directions.
I quickly took a snap as it was so weird, and just as I thought aliens had taken over them, someone hidden away shouted: "And... action!" And all the extras started to move for a now visible camera.