Britain’s Conservatives have begun their annual conference, with Europe threatening to spoil the party. Leader David Cameron was hoping for a united front to show his team is ready for government. But London mayor Boris Johnson’s calls for a referendum on the Lisbon Treaty re-opened old wounds.“I think what Boris is saying is what I am saying,” said Cameron. “We all want a referendum on the Lisbon Treaty. We feel cheated that we haven’t been given one, even though the government promised one. We feel angry that the Irish get to vote twice on the treaty and we don’t get to vote once. And Boris is saying what I am saying, that we want to have that referendum, and we want to make it happen.” Johnson is a committed Euro-sceptic, and has often irritated senior Conservatives by off-the-cuff comments, sometimes at odds with party policy. “It is a tricky one,” he said. “What I can say… I do not know if I should have answered this question at all about this b****y referendum; there is no answer.” All the polls say the Conservatives will win the election next Spring. But Cameron knows anything can happen in politics, and he’s taking nothing for granted. “Let this be the week we don’t just let Labour lose election, but we show we deserve to go out and win it,” he said. Europe has threatened to tear the Conservatives apart before, and Cameron will be desperate to keep both sides of his party happy. That may mean talking about a referendum, but leaving a decision until the very last moment.