The government is to carry out a 'root and branch review' of Britain's armed forces, led by Tony Blair's former defence secretary - and former NATO boss - George Roberson. He says the UK is facing a 'deadly quartet' in the shape of Russia, China, Iran and North Korea. Our guest, Ed Arnold, Senior Research Fellow in European Security at RUSI, tells us it all hinges on if and when the West faces conflict with Russia. Hosted by Caroline Hepker and Yuan Potts.