Events are the ephemera of history; they pass across its stage like fireflies, hardly glimpsed before they settle back into darkness and as often as not into oblivion. Every event, however brief, has to be sure a contribution to make, lights up some dark corner or even some wide vista of history. Nor is it only political history which benefits most, for every historical landscape - political, economic, social, even geographical - is illumined by the intermittent flare of the event.