Why Australia wants nuclear submarines

In as little as four years' time, US nuclear-powered attack submarines will be deployed to Australia, the government says to keep us safe. They're the length of a rugby pitch and can cruise through the water in almost complete silence, and the price tag is mind-blowing too: up to $368 billion over the next 30 years.  Today, the ABC's political editor, Andrew Probyn, on how fear of China has driven us to the biggest defence investment in our history.  Featured:  Andrew Probyn, ABC political editor