Mr Cameron is going to need all his powers of persuasion when he gives a key note speech in Manchester today on the state of the economy. It won't do just to blame it all on the wretched euro. It scarcely needs repeating that despite our apparent advantages outside the eurozone, the UK is back in recession, with output still some 4pc below its pre-crisis peak. Germany, on the other hand, has recovered all its lost output and is still growing robustly. For Mr Cameron to claim, impotently, that we are powerless before the storm will only invite ridicule.