Kim Darroch, Luke Harding and Mark Leonard talk to Katya Adler

Have we relied too heavily on the US to protect us? How much of a threat do Russia and China pose to UK security? In a changing world, have we left ourselves exposed? The BBC’s Europe editor, Katya Adler, talks to former national security adviser and Britain’s former ambassador to Washington Lord Darroch, the Guardian’s foreign correspondent Luke Harding, and author and director of the European Council on Foreign Relations Mark Leonard.