There’s a 500-foot crack in the concrete floor of Tate Modern. “I’m with an architect and a couple of builders, and we are examining the crack from a wide variety of angles and sticking our fingers inside and giving it a damn good poke and generally trying very hard indeed to work a few things out. The first is: how on earth did it get here? The second is: could it be dangerous? This being the Tate, we also feel obliged, finally, to consider the possibility that it might be art.”