For thirty years civilization hung by its finger- nails. In the abyss below - tens of thousands of mad missiles waited - poised to roar up at the whim of a hair trigger. For three decades, every day, every hour, catastrophe flicked its tongue at humankind. One slip and the blackened flesh of a hundred million men, women, children would peel off white bone; and nuclear winter lay in wait to devour billions more.

By the greatest good luck, and the slimmest of margins that danger passed. The world, on the brink of the volcano, did not trip. The most ferocious horror ever to open its jaws to the human species, retreated innocuously. We walked in the valley of death and lived.

How do we now mark that deliverance?