Looking at the UK, reunified Germany and the European Union, the former Conservative Cabinet Minister John Redwood MP asks how successful a currency union can be without political union behind it.
After the travails of the eurozone in the wake of Irish, Portuguese, Spanish and - above all - Greek woes, John Redwood argues that the pressure is growing on the countries which use the euro to move closer politically. But not everyone in those countries agrees, as he discovers.
Meanwhile, in the UK, leading Scottish Nationalists continue to make the argument for Scotland to become independent while retaining the pound. But how sustainable is this position? And what are the lessons of the decision by the German government to bring together the old East and West using a currency union that valued both countries' currencies at the same rate despite a huge gap in the productivity between the two?

Producer: Simon Coates.