The morning light filters through the rooftops and into a slim sunlit alleyway in Istanbul’s Grand Bazaar, and the currency traders who provide a bellwether for the Turkish economy arrive. Each is clutching at least two mobile phones, along with glasses of bitter Turkish tea and packs of cigarettes. There are stacks of mobile phones on a nearby ledge, ready for currency trades yelled into them at speed. The mood is palpably tense, cresting into a wave as trading opens and the entire crowd filling the alleyway swiftly transforms into a frantic bidding war. “Is anyone buying dollars?” yells a...