With recent events in Nice, Munich and Reutlingen, and today's apparently terror-related brutality in Normandy, one thing becomes very clear.
If European governments don't very quickly address their mismanagement of migration, more national leaders will shortly face calls for Brexit-type referenda, if not on EU membership, then at least on freedom of movement.
The existing EU policy on movement doesn't work in the age of sudden mass migrations, any more than multiculturalism has worked as government policy.
German Chancellor Angela Merkel acknowledged the latter a while back. Where both Germany and the wider Europe is concerned, she must now also admit that an open-door migration policy toward people from war-torn regions, whilst well intentioned, is not sustainable. Neither is it popular: more than half of the German population disapproves of it.
Mrs Merkel, normally a skilled political pragmatist, must also recognise the glaring weaknesses this policy has revealed in the EU's freedom of movement principle, as it currently stands.
The Chancellor and other European leaders should now advocate a radical reform of this fundamental EU policy.
The failure of freedom of movement in the wake of mass migration should also sound the death knell for the federalist dream.
Clearly, Europe needs the benefits of free trade, with a degree of shared regulation to govern it.
However, plans for the effective removal of borders altogether and the birth of a single political oversight, which would render national governments redundant - or at least reduce them to the level of devolved regional bodies - are now shown to be unworkable.
These lofty notions have favour with very few Europeans - apart from a class of full-time Eurocrats. Many of the latter are arguably driven more by ideology and self-interest than by pragmatism or the pursuit of the common good.
If the EU does not reform - deeply and rapidly - its internal credibility will erode as quickly as the recent political earthquake overtook post-Brexit British politics.
Its global standing and support will wane just as quickly. Such a scenario would impact on the post-Brexit UK, too. The strength of our trade with the EU relies on its internal stability and the desire most Brits share to retain relatively free access to travel within the EU will not be achieved if Europe moves too far to the right as her people grow frustrated with instransigent, arrogant or sort-sighted leadership.
Europe's future, as a potential global hub for innovation, collaboration, economic growth and political stability must not be held to ransom by the federalist dreams of a few professional - often unelected - Eurocrats.