For the first time in a generation, the possibility of Britain leaving the EU is on the mainstream political agenda.
This report is by political editor Tom Bradby:
To the surprise of many Lib Dems, Nick Clegg appears to have played down the importance of the Coalition's divide on an in-out referendum.
Business leaders in Davos are worried about the Prime Minister's pledge to put Britain's membership of the European Union to a referendum.
With some in France keen to "roll out the red carpet" for a British exit, Germans favouring decentralisation welcome EU renegotiation talks.