In December 2000, the Spanish artist Santiago Sierra paid four people to have a line tattooed on their backs. As Sierra explained it: “Four prostitute(...)

 A poster hangs on a wall in Ebrington Square, Derry, the venue of the 2013 Turner Prize. Photograph: Getty Images

Everybody I know with a reputation for knowing anything about art appears to believe that Tino Sehgal is a shoo-in for this year’s Turner Prize. The f(...)