Europe is getting jittery. Soon the borders of the European Union will stretch from the Atlantic to the Black Sea, bringing the population of the world’s biggest trade bloc to almost 490m – bigger than the US and Japan combined.

Seen from some European capitals, the accession of Bulgaria and Romania in 2007 or 2008 is a worrying sign of overstretch, fuelling fears that the EU is becoming too cumbersome and too diverse to have real clout in the globalised world.