In more general foreign policy matters -- from diplomacy to the deployment of development aid -- the U.K. is already far more involved in Europe-wide affairs than its disengaged image would suggest. In fact, research from European Council on Foreign Relations' own Scorecard project suggests that the U.K. is up there with Germany and France (and, remarkably, Sweden) as a leader in European foreign policy, on issues ranging from Iran nuclear ambitions to Somalia. Maybe that's why Barack Obama himself has been nudging Britain to stay in the EU.

Economics matters are more complex, and there are doubtless many Europeans, from Paris to Marseilles, who might be pleased to see Britain leave the EU. But despite its own current economic woes the British economic vision of more open, competitive economies is something that chimes in Berlin and several other corners in the northern half of Europe. Without a British counterweight to help balance the more statist economies within the Union, the EU might not be quite as popular in Stockholm and Warsaw. After all, growth is a massive problem in Europe, and one of the core reasons why the euro crisis became so critical (one startling recent figure was that Italy experienced less economic growth in a decade than anyone else in the world other than Zimbabwe and Haiti).

This is not to ignore the problems that Britain's opposition to "ever closer union" could cause the rest of the EU. Even Cameron has argued that the eurozone needs to integrate further if it is to survive. And if the euro does not survive the current crisis, any hope of a fighting fit 21st century Europe is probably dead in the water anyway. But Cameron obviously believes that it can survive, and that Britain can help Europe reform and become stronger.

All of this will not have escaped Angela Merkel's notice as she makes her careful calculations. Britain's recent bumptiousness may grate, and certainly creates extra problems for those already struggling to work out exactly how the sticking plasters currently attached to the eurozone can be converted into more sustainable long term cures. But losing Britain could become something of a nightmare for many other Europeans (provided the price is not too high), and Germany will be crucial in brokering any deal that keeps them in and helps make the EU fit for purpose in the 21st century. A plea for this seems to be the subtext to Cameron's speech: Britain doesn't want to turn away from Europe, provided the EU doesn't want to turn away from the world.