So everyone will be obliged to leave.”In the event of an eruption,” Antonio Bassolino told The Independent, “the authorities have the responsibility for arranging the evacuation of 581,000 residents and distributing them around Italy, at a cost to the public administration that could be as much as between €30m [£21m] and €40m [£28m] per day.”It’s a challenge that would widen the eyes of a regional governor anywhere in the world, let alone in southern Italy, where respect for the forces of law and order is notoriously shaky. Because, just as the destructive ferocity of a new eruption remains impossible to predict, there is also no way of knowing which towns will be in the firing line. The vulcanologists will study their data, draw their conclusions and make their announcement. And then the government of Antonio Bassolino will have to do something about it.That means evacuating everyone in the Red Zone. The tremors and the ominous belches from the volcano’s depths will one day resume. It’s a lazy government’s way of filling a budget hole in a hurry.But when Vesuvius clears its throat again, all these people, legal or otherwise, will have to go. The buildings steal up the steep slope towards the crater, like a mortal game of grandmother’s footsteps.All of them are illegal: abusivismo, as illegal construction is called, is the plague of modern Italy, ignored by weak governments, sponsored by organised crime gangs such as the Camorra (the Naples equivalent of the Mafia), and producing a sense of impunity in its perpetrators that grows bolder each time the central government declares an amnesty A new one has just been announced.

But that hasn’t stopped them.Up here on the volcano’s slopes, the architectural styles vary: bunker-like homesteads thrown together from breeze blocks, protected by dogs and surveillance cameras; blocks of flats that would not look out of place in town; a single elegant Modernist villa of plate glass and steel, set in a generous garden of oleanders and umbrella pines. The slopes of the mountain constitute the Vesuvius National Park: no one’s supposed to build here at all. This month it publishes a plan to offer €30,000 (£21,000) to any household willing to move.It’s not just the ranks of high, crude, concrete apartment blocks, lining the narrow streets all the way down to the bay, that pose the problem Development continues far up the volcano’s flanks. It has set itself the challenge of persuading 150,000 of these people to move out of the shadow of Mount Vesuvius and make their homes elsewhere.

And it’s this crazy overcrowding that has persuaded the Naples regional government to take drastic measures. Altogether 18 towns hug the volcano’s flank, and they have been growing with a zany, idiotic energy – and the encouragement of the authorities – since the last eruption in 1944.Today the Red Zone is home to nearly 600,000 people. Squashed between the volcano and the sea, modern Ercolaneo and Pompei, as well as other towns along the bay, have swollen into a single, densely congested urban mass. It has been the subject of a thousand prints and etchings, landscape paintings and picture postcards.But today the whole region under Vesuvius – the Red Zone, as it is known – has become a huge overspill suburb for the city of Naples. To understand why, it is enough to stand on the volcano’s southern flank and cast an eye around.

It’s one of the most famous vistas in Italy, the stupendous purple volcano climbing up towards the sky, the sparkling blue of the Bay of Naples beyond, the towns and vineyards dotting the narrow plain in between. Vesuvius, says Antonio Bassolino, the President of the Naples region, is “the most carefully monitored volcano in the world”. Notice of the next great event should arrive some months before it happens.But that’s when the trouble will start. This time around, nobody is going to get caught by an eruption the way ancient Pompeii was. bulging and uncoiling”, as Pliny the Elder wrote, “as if the hot entrails of the earth [were] being drawn out and dragged towards the heavens”, was totally unexpected. That’s why the population died where they stood: gassed, pelted with pumice, buried in stone, sand and ash in the midst of their daily lives (as vividly described by Robert Harris in his new novel, Pompeii).Now, 1,924 years later, we are much better informed about Vesuvius, but not necessarily a great deal wiser. They didn’t realise that it was responsible for the earthquake that 17 years earlier had killed hundreds and partially destroyed their town.
The stunning column of fire and stone that came roaring out of the bowels of the volcano on that August afternoon AD79, “thrusting…