Eternal city's Notte Bianca pitched into darkness as power cut turns the lights off all over Italy

This was to have been the night Rome came alive. The city's ambitious left-wing mayor Walter Veltroni, building on the success of earlier cultural initiatives such as the "Roman summer" festival, proclaimed the night of 27 to 28 September Rome's Notte Bianca, its White Night.

The Eternal City was going to rock from dusk to dawn. Museums would not close, and would serve coffee and buns to punters turning up after 3am. Monuments including the Colosseum would throw open their gates to all, for nothing. On the spot, in the piazza today known as Largo Argentina, where Julius Caesar was stabbed to death, Shakespeare's play would be performed. Relays of athletes were to race non-stop round Piazza del Popolo.

With its triumphal arches and its circuses, Rome arose as the great open-air stage of emperors and went on to become the theatre of popes. Readers of Conde Nast Traveller recently voted it their favourite city in the world.

As a place to live, it is scarcely convenient but as a stage for the authorities to strut and preen it is nonpareil, always has been. They had scheduled Beckett at midnight, fireworks on the Terrazza del Pinicio. Rome was flaunting its eternal virtues, its urbanity and elegance, the dolce vita which has always been 10 per cent image, 90 per cent substance.

Then, suddenly, shortly after 3am, everything went horribly wrong. The night, balmy and close, turned abruptly to heavy rain. Then the power failed. And on the marvellous city-wide stage, the curtain of darkness dropped.

A million and a half people - drunk, scared, worn out, ready to drop, soaking - were plunged into blackness, the crowds swarming the city streets, packed on underground station platforms and in trains stalled between stops.

Rome's revellers were the unluckiest of 57 million Italians, from the Austrian border in the north-east to the far end of Sicily, to suddenly find themselves without power. This was the latest in a string of sudden cuts that have hit the US and Canada, Italy (once before), Denmark, Sweden and Britain.

Excluding Italy's summer scare, the power cut was the first to strike the nation's grid for more than 20 years. The summer crisis was smaller, more understandable, well trailed and carefully managed. It was in June, during the summer heatwave, when unprecedented use of air conditioners conspired with a drought that shut hydro-electric plants to bring the system to the point of collapse.

In June, too, the lights went out, but the risk had been aired, and the pain was rotated from zone to zone and region to region. The system, the authorities implied, might be under strain but it was also under control. Further advance warnings were given in subsequent weeks, but no cuts followed.

But on Sunday morning, the blackout (Italians use the English word) was unannounced, total, except for Sardinia, and almost simultaneous through the country. By 9am, when much of the north was clambering to its feet again, the first explanations were being offered.

Again, as in June, it appeared to be the fault of the French. Italy imports 20 per cent of its power from France, a dependency that grows increasingly controversial every time an event like this happens. June's blackouts were blamed on France, claiming they reduced their risk of summer shortfalls by cutting supplies to Italy.

But yesterday's shutdown appeared to be a freak accident. As usual, the explanations seem impossibly flimsy to a layman. Two lines carry power from France to Italy, the main line and a back-up. Both packed up simultaneously. Hence the catastrophe.

A spokesman for Italy's national grid said it lost control of power flowing through the system for no more than four seconds, but long enough to trigger a domino effect through the country. Italy's Minister of Industry, Antonio Marzano, said at a press conference: "The breakdown was not the result of anything that happened in Italy, but a succession of circumstances originating in Switzerland. The blackout has causes yet unknown which had the effect of isolating France from Austria and Italy." Shorter power cuts were also reported last night from Austria and Croatia.

Andre Merlin, the director of France's national grid, said the fault originated in Switzerland, probably due to a storm, and caused a short circuit; the problem, said the director of the French national grid, Andre Merlin, "was eliminated well in France but wasn't correctly eliminated in Italy". But such details mattered little to the suddenly sober Romans, stumbling, sopping wet, through the pitch dark after the brutal conclusion of their party night.

From the lofty heights of the mayoralty, the event had already been declared a famous success shortly after it began. The White Night was "a festival against wickedness", Walter Veltroni told the crowd, two hours before darkness struck. "Tonight the city lives with a particular kind of magic, it recovers a part of its life."

But for the plebs on the ground, that had been a dubious proposition long before the heavens opened and the night closed in; this latest reworking on the "bread and circuses" theme was looking a tad misconceived to many people right from the outset.

Every popular location in the city - Michelangelo's wonderful piazza, the Campidoglio, the Colosseum, the antique ruins in the Roman Forum, the Via del Corso - was hideously congested from 9pm; merely moving through the streets, never mind going to a museum or a play, was a challenge, like fighting through the crowd leaving a football match.

No restrictions had been placed on cars in the city, so the city's traffic, never smooth-flowing, was snarled as rarely before. The subway, buses and trams were declared free after 10 pm, so towards midnight, Romans were suddenly discovering what it feels like to be a commuter in Tokyo. And not liking it much.

Then the rain came and the power failed. In Rome alone, the fire brigade helped people in 180 trapped lifts to safety. Up and down Italy, 110 trains stopped, trapping 30,000 travellers on the tracks, thousands of them under the streets of Rome, on a night when 12,000 people had used the subway. At Colosseum station, home of the original circus, the crush was frightening and intense, the emergency services said. One man suffered a broken leg as the crowds struggled through, the only reported casualty.

But Mayor Veltroni managed to sustain the elevated rhetoric with which he had inaugurated the White Night. "What happened tonight in Rome," he said, "I see as testimony to a maturity, a sense of solidarity, of which we have seen many signs in the past."

This is a vain city; many Romans will be content to bask in their Mayor's good opinion. For many others, Italy's black night raises of awkward questions about the ability of this country, bobbing on a sea of self-conceit, to do what it takes to stop such breakdowns becoming routine.

How the rash of power cuts has spread this year

SCANDINAVIA

Widespread power cuts in Denmark and Sweden left nearly four million people without electricity for three hours on Wednesday. Traffic jams brought Copenhagen to a standstill, aircraft were diverted and the new driverless subway was suspended. A faulty transmission line serving both countries was blamed.

BRITAIN

A blackout in London paralysed most of the underground system and main rail terminuses during rush-hour on 28 August. The National Grid said the blackout, which also cut power to homes and businesses in south London, was caused by two incidents in a network of substations.

NORTH AMERICA

More than 12 million people living in north-east America and Canada were affected by a series of blackouts on 14 August. US officials said that the blackouts, which cut power to subway trains, six major airports and ten nuclear power stations, were caused by a failure at a Manhattan power station.