Today's back-to-school headlines illustrate the perils facing the Prime Minister on Europe. Downing Street has denied German claims that David Cameron said Britain would leave the EU if Jean-Claude Juncker is chosen as president, but that hasn't stopped them being widely reported. In reply Mr Cameron has been accused of "blackmail" by Mr Juncker (btw, someone really should do an audit of his time as the finance minister of Luxembourg who consolidated its reputation as a force in the murky world of tax arbitrage). "Stick it up your Juncker" is the Sun's groaner. Accompanying the headlines is a sense that Mr Cameron has gone public too early on Britain's opposition to the Luxembourg federalist. Ian Traynor makes the point usefully in the Guardian.