I'd say an issue like the EU, and whether we're in it or not, is pretty massive. In addition to that, it's been a pretty big issue for a while now. UKIP have been on the rise for a good couple of years, and even if they don't continue to grow, they're going to get a substantial portion of the vote this time, and got the biggest portion of the vote in the EU elections. When you're having EU elections and the most voted party is one which wants to leave, I'd say there's a decent mandate for a referendum, especially when it's quite clear that a lot of people feel passionately about it.