It's been one of the longest running questions for New Zealand business: would Rio Tinto pull the plug on the Tiwai aluminium smelter? Today, we found out the answer. Rio Tinto, the majority owner of New Zealand Aluminium Smelters, announced it was moving to close the smelter. It immediately sent power company stock prices into reverse, caused ripples through the New Zealand economy and the Southland region. Business reporter Emma Hatton has the details.