That it's also a vent. The world will have seen it. But not seen it. Because it's just around the corner from the London "branch" of Occupy Wall Street in front of St. Paul's Cathedral. London Walkers see it. And see it. On, for example, Adam's Ghosts of the Old City Walk on Tuesday night (7.30 pm, St. Paul's Tube). On their way to haunted and haunting London.