DJ: Dan, you've argued in books and speeches for a straightforward referendum: in or out? But what about you, Nick?

NB: I'm actually a genuine believer in referenda so if there was a growing swell of opinion for one I wouldn't be against it, but it's not something I feel very strongly about either way. I wouldn't support the proposal to get out because I do believe our interests are common interests, and the benefits of having common interests are just about greater than the problems caused by the EU. And I do believe, maybe naively,  that the Thatcher government did show you can make it work, and make it work for Britain. It requires a particular attitude which she had, and which no prime minister since then has had until, I hope and believe, David Cameron. So I would be against pulling out but in terms of having a referendum I'd be relaxed about it. I feel it would be cathartic for the nation to have a moment to decide and really go through a process and come to an answer.

DJ: But could the coalition survive that? 

DH: The hilarious thing is that an in-or-out referendum was, in fact, Lib Dem policy. It tells you a great deal about our political culture when almost all observers now say that it's the Lib Dems who would resist the implementation of their own manifesto pledge; everyone just takes it for granted that such promises are meaningless. Perhaps I'm being terribly innocent about all this but, instead of starting from what you think the outcome of such a referendum would be and then working backwards, what about asking in principle whether the EU is the sort of issue where it's proper to consult the country in a plebiscite. The idea that referendums are alien to our system of representative democracy has been blown out of the water. Until 1997, we'd had only four such votes: one each in Wales, Scotland and Northern Ireland, as well as the Common Market referendum in 1975. Since 1997, we've had a further 45, some on pretty trivial issues. We're about to have a national ballot on a technical change to the voting system — a change, by the way, which neither of the two coalition parties proposed at the last election. The Tories were clear in their support for first-past-the-post, the Lib Dems in theirs for STV. Neither suggested AV. Yet at the same time we're being denied a referendum on Europe, which all three parties were recently promising. If you were asking in the abstract what kind of question would be appropriate for a referendum, EU membership ticks every box. Is it an issue of major constitutional importance? Yes. Does it involve the location of power? Yes. Does it divide the parties internally? Yes. Is it the kind of issue that cannot easily be settled at a general election? Yes. All our constitutional authorities — Bagehot or Dicey or Erskine May — would see this as a textbook case of where a national ballot is proper. The only argument against a referendum is fear of the result and, in a democracy, that is no argument at all.

NB: I think that would be true if you were saying that was the only reason not to have a referendum ever. I wouldn't support having one now because I think the logic is to do it when there's a change on offer — that's why the logic of having a referendum over the Lisbon treaty was so strong. I think that the natural way that it would occur is that if there were say a further treaty which proposed further transfers of power and sovereignty, that there would be first a referendum on that treaty which presumably the Conservative Party, certainly I, would be arguing that we should be voting against. If that was then successful and the British people rejected that transfer of powers there would then probably be some form of a crisis within the European Union at which point it would be natural to say this might be the moment to have a bigger question about the thing. I think that's the logic of it.