For as long as I can recall, our country has been defined by what we might call three basic truths that we hold to be British: first, our devotion to liberty, tolerance and the rule of law; second, our instinct for fairness; and third, as an island and trading nation, our commitment to engaging with the world. And while in the heat of an election battle it is difficult to see beyond the claims and counterclaims about tax, spending and migration, it is clear to me that far, far more is at stake on 4 July than what is conveyed...