Europe’s foreign policy supremo, Federica Mogherini, is off on a mission even more difficult than getting Iran and the US to agree their nuclear deal, writes Denis MacShane.

Denis MacShane is the UK’s former Minister for Europe and the Balkans who visits the region regularly.

Mogherini is in the Western Balkans which still more than 20 years after the worst post-war mass murder of innocent citizens at Srebrenica remains Europe’s most problematic region.