AP Photo

Britain has never been too keen on tying the knot with Europe. It sat aside in the 1950s as Germany, France, Italy and the Benelux countries forged a single market in coal and steel, which became a broader common market. It eventually joined, in 1973, largely because Europe seemed to be where the money was. Britons still think of their relationship with Europe as a transaction. But their feelings about the costs and benefits of membership have changed utterly. Europe is no longer the thriving economic club that Britain joined 40 years ago. The euro-zone crisis has exposed the lack of dynamism in much of Europe (though Britain itself is hardly booming) and the British also feel sidelined, as countries that use the single currency are pulled more tightly together. Britons have come to...