Ken Carroll is challenging a basic tenet in the global economy: that we all need to learn Mandarin Chinese to conquer the world’s largest market – but that learning Chinese is boring. Mr Carroll, a Shanghai-based language teacher turned internet entrepreneur, says that does not have to be so: he has pioneered a painless podcast method for learning Mandarin, and nearly a quarter of a million people worldwide are using it on Chinesepod.com, which sends daily Man­darin lessons to iPods and Google phones around the world.