<p>The Privy Council is a centuries-old institution - yet, for an entity with such extensive influence over Britain's history, we know relatively little about it. What exactly does it do? To whom is it accountable? Just how much power does it hold over us? Some say it has no power at all, although you might not agree if you'd been sentenced to death in a former British overseas territory that still used the Judicial Committee of the Privy Council...