Be wary travelling home late on the Piccadilly line when you are tired and maybe preoccupied with those arguments at home, or the quiet desperation of your job. Be wary on those nights where the motion of the carriages rock you back and forth and the air is a fug of tunnel smell and sparks, and all you can see in the window opposite is your reflection against the dark, staring back at you like somebody already lost. 

Because if you fall asleep between stations, on certain nights when the moon is in the right place, you will wake with a start as the driver announces ‘this train terminates here’. You’ll curse at yourself and you’ll grab your bag and stagger bleary-eyed off the train. As it pulls away, you’ll realise, puzzled, that you are not in Cockfosters, nor are you in Uxbridge, Heathrow or Rayner’s Lane, and when you stare at the map on the wall of the empty platform, you won’t recognise a single station name.

You are travelling on the Other Lines now. Can you find your way back?