At last the real debate about Britain’s place in Europe is about to crystallise. From the day the UK joined the common market, the conflict between its desire to maintain a club of sovereign nation states and the clear objective of other European countries to forge “ever closer union” has never been resolved. The eurozone crisis has forced that divergence of interests into the open. David Cameron, the prime minister, should seize this moment to establish a new deal for Britain.

The euro project was always as much about advancing the cause of political integration as it was about economics. As is now clear, a single currency encompassing disparate economies can work only if it is managed within a common fiscal and political union, where the more prosperous areas agree to subsidise the weaker ones. That requires consent to a common federal structure, administered by a legitimate central authority.

That has always been the objective of the EU leadership – most transparently in the drafting of the EU constitution which, having failed to win consent, was enacted almost unchanged in the Lisbon Treaty.