Russia's president Vladimir Putin has been criticised in the West as a ruthless authoritarian ruler determined to revive imperialist ambitions. But is it a mistake to invest President Putin with such transformative power and strategic vision? Russian journalist Mikhail Zygar has written a book about the powerful groups of people around President Putin and their influence on decision making. HARDtalk's Stephen Sackur asks Mikhail Zygar just how firm is Vladimir Putin's grip on power and what does it mean for Russia's future?