The dramatic crack created in the floor of the Tate Modern Turbine Hall by Colombian artist Doris Salcedo is, in places, waist deep. The exhibit was opened in early October. Perhaps it should also have run up (or down) the actual south wall of the space, which divides off the remnant power generating installation, still distantly audible. In architectural/engineering parlance that would represent a 'shear crack'. And Salcedo's agenda is a political one, partially inspired by issues of human rights, rendition and the tragedy of Guantanamo. It could all also be said to comprise a crack (sic) at the institutionalisation of the arts. Will there be claims by an enthralled public for sprained ankles, or further along the crack for 'stuck' children? Or for wrenched limbs? Salcedo remains honest about her inspiration, but perhaps oblivious of the risks.