Leonid Volkov - Chief of Staff to Alexei Navalny

Russian opposition leader Alexei Navalny is the most resilient opponent Vladimir Putin has ever faced. Navalny survived assassination by Novichok, returned to Russia and is now in a prison cell. Stephen Sackur speaks to Navalny's chief of staff Leonid Volkov. The opposition movement has supporters willing to take to the streets in anti-Putin protests in Russian towns and cities; but do they have a strategy capable of forcing Putin out of power?