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Europe referendum then and now

How did Harold Wilson do it? That's what David Cameron may be wondering as he puts the finishing touches - yet again - to his speech on Europe. Back in the mid 1970s Wilson returned to power promising to renegotiate Britain's terms of membership of what was then called the European Community. And having achieved his aim, he put the new terms to the electorate in a referendum and won with a huge majority. The former diplomat Sir Stephen Wall is the author of ''The Official History of Britain and the European Community.' Volume II, 'From Rejection to Referendum,' has has recently been published and explains in detail why the Labour Party under Harold Wilson, having supported membership of the Community, threatened to take Britain through the exit door unless the terms of entry were changed. I asked Sir Stephen Wall why did Labour end up promising a referendum?