Slowly they started to appear, furtive, scuttling in the shadows. The clock at the top of the station roof ticked closer to the allotted hour, and still they came.
Most wore grey, some black. In some areas they clustered together, small groups huddled in dark corners, their breath mingling in the cold air.
Gradually, their numbers increased, a plague of spectral figures, drawn by an invisible force towards some unknown purpose.
The clock hands moved inexorably toward the moment of truth and suddenly they paused before there was the sound of the world’s largest umbrella unfurling – flash mob indeed.