In or out? For the next five years Britain's future in the European Union will be shrouded in uncertainty thanks to David Cameron's commitment to a referendum. He believes his dramatic gamble will pay off not just at home, but in Europe too - allowing him to recalibrate Britain's relationship with Brussels. Will it work? HARDtalk speaks to Sir Nigel Sheinwald who was the UK's top diplomat at the EU, foreign policy adviser to Tony Blair, then Ambassador in Washington. Is the Cameron EU gambit in Britain's national interest?