Australian politics has turned backstabbing into an art form. Thanks to yet another internal party coup, Malcom Turnbull has become the country's fifth Prime Minister since 2010. The political turbulence comes at a tough time - the Australian economy is being hit hard by the slowdown in China and the slump in global commodity prices. Stephen Sackur talks to the billionaire mining magnate Andrew Forrest. Has Australia squandered the riches that came with the resources boom of the early 21st Century?(Photo: Andrew Forrest, chairman of Fortescue Metals Group)