I’m told it’s bad luck to pass someone on the stairs. Here at the Office, groups of otherwise intelligent people will cluster at the bottom of a reasonably wide staircase looking patiently upwards as a single person of average build slowly descends. Likewise, the same kind of people – they’re all fairly intelligent here; we don’t employ slack-jawed fools – will gather at the very top of the aforementioned staircase as someone (maybe the same person that was previously descending, maybe a different person altogether) slowly ascends. Often with a hot beverage.

Risk of an incident of scalding apart, why wait? Why not just continue the flow, up and down, ascend and descend. We have no irrational fear of passing one another in relatively narrow corridors, or through doorways, or whilst driving on narrow, twisty roads with irregularly-spaced ‘passing places’. What sets stairs apart? What mysterious quantum process is triggered by passing another person on the stairs?

Moreover, does it apply in public situations such as the 3-abreast stairs that descend to the level of the Metropolitan and Circle Line at Kings Cross Tube Station? Hundreds, nay thousands of people pass one another on those stairs every day. Does each one of them suffer bad luck? Perhaps the bad luck quanta ejected by the constant stair-passing are too confused by the maelstrom of commuters to finally settle on any one individual. Maybe the cloud of bad luck particles drifts aimlessly along the tunnels of the London Tube system, blowing a fuse here, tripping a set of points there, causing untold misery to tourist and tout alike.