Prime Minister David Cameron thought that his promise to renegotiate the terms of Britain's membership of the EU, and to hold an in-out referendum on British membership in 2017 had bought him domestic political peace. Instead, many in his own Conservative party are agitating for an even harder-line position, and the anti-EU United Kingdom Independence Party is soaring in opinion polls. An eventual British exit from the EU is looking increasingly possible. So what's going on, and what do other Europeans make of it. Quentin Peel in Berlin joins Janan Ganesh and Gideon Rachman in London.