Thirty years ago this month the Soviet Union’s hold on the Warsaw Pact countries of eastern Europe began to crumble. Though no one knew it at the time, what started as a small revolt quickly turned into the death throes of an empire.

On August 19, 1989, enterprising Hungarian dissidents and their Austrian supporters organised a border picnic to mark the removal of barbed wire and machineguns from that part of the Iron Curtain. Amid the festivities, hundreds of East Germans fled to the West — a harbinger of the thousands who voted with their feet later that autumn, as they flooded into Prague in the hope of reaching the West. That tide not only doomed the communist regime in east Berlin but its similarly