This week marks the 100th anniversary of one of the most influential lectures ever given on politics: Max Weber's 'Politics as a Vocation', first delivered in Munich on 28 January 1919.  David and Helen talk with Jonathan Powell, Tony Blair's former chief of staff, about some of its lessons for the age of Brexit.  Where have all the good leaders gone?  Is the party system to blame?  Are we suffering from an excess of conviction or a lack of conviction?  And who will be responsible if we see a return to violence?  Recorded before a live audience at Trinity Hall, Cambridge.