For as long as the risk of sovereign debt default was limited to small countries such as Greece, it was always possible to stumble from one EU meeting to another, in the hope that something might turn up. But the danger of contagion was always there; and now that Spain has edged closer to the precipice of national bankruptcy, we may well be reaching the moment of truth for the single currency. This is, then, an appropriate moment for Mr Cameron to be meeting Angela Merkel, the German Chancellor, as he will tomorrow. If any plan is to be agreed, then it is in Berlin that the decisions must be taken. Yet it is also in Berlin where the central problem lies.