What could be the starting point for EU collapse?

Press quote (Sputnik News)
05 January 2016

"Given that by any objective measure the EU is in a terrible mess, I’m shocked that the 'in' campaign is still getting half," Charles Grant, director of the London-based Centre for European Reform.

If Britain finally leaves the bloc this would have no precedents in the history of the EU. This will reverse what had been seen as the inexorable expansion of the union to bring peace and stability to the "historically bloody lands of Europe."