Deploying troops overseas, whether to fight or protect, is a costly business. It is one of the reasons why throughout history, wars and long term military commitments have often been contracted out to private operators – mercenaries – whose methods, personnel and costs can be very different. HARDtalk’s Stephen Sackur speaks to Erik Prince, the founder of the Blackwater security contractor used by the US Government in Iraq until things went badly wrong. A decade on, he is pitching to replace the US military in Afghanistan – is it an idea President Trump might just buy?