If a unified euro-core does develop, it will be a fundamental change. It may be incremental, and take years, but no one should doubt its impact. It is also an opportunity. If an inner core can radically alter its relationship with the EU as a whole, then non-core members may feel free to do the same. I believe they should. There is a bargain to be struck. Our relationship with Europe has been a running sore in British politics for more than half a century. The opportunity is coming to settle on one that is more amenable to our interests and our instincts.