Iran seldom admits the international media. It makes an exception at election times because it wants the world to see the Islamic republic's glorious democracy in action. Thus some 400 foreign journalists and television crews were given ten-day visas to cover Friday's presidential election, and for a week we really did see a vibrant and impressive democratic process.

Admittedly the four candidates were handpicked by the regime, but they ranged from the liberal to ultra-conservative, offered starkly contrasting visions for the future and engaged in remarkably outspoken TV debates. The people responded. Armies of supporters took over the streets, festooned every square with posters and banners and, on election day itself, flocked to the polling stations in numbers that shamed most Western democracies.

The charade ended abruptly on Friday night. Scarcely had polling ended than Mahmoud Ahmadinejad's cronies in the Interior Ministry and Elections Commission declared him the winner. They gave him not a razor-thin victory, which might just have been credible - the President did have legions of diehard supporters among the pious and rural poor. They gave him nearly two thirds of the vote, a figure that defied belief and raised two unmistakable fingers to the Iranian people and the world. They claimed that the main challenger, Mir Hossein Mousavi, lost heavily even in his own village. The number of votes allegedly cast for Mr Ahmadinejad, 24.5 million, was probably chosen so that he could claim to have more support than any president in the republic's 30-year history. The previous high was just over 20 million, cast for the reformist Mohammad Khatami in 1997.

The crackdown began instantly. Mobile phone and text messaging systems were taken down so the opposition could not organise. Opposition websites and international news services were blocked. Baton-wielding security forces flooded on to the streets. Overnight the festive atmosphere turned to fear, exuberance to terror, as the regime showed how evil it is.

All weekend protests were ruthlessly suppressed. Demonstrators were beaten. Foreign journalists, including a reporter and photographer from The Times, were detained. Leading reformists were arrested. Iran's “Prague Spring”, its “Velvet Revolution”, was crushed with Soviet-style ruthlessness by a regime practised in silencing dissent. Mr Ahmadinejad, the self-styled man of the people and champion of the oppressed, unleashed the full force of the state machinery on his own population. Meanwhile, congratulations poured in from... well, Syria and Venezuela.

Why the volte-face? Why did the regime open the door a crack, only to slam it shut so violently? Almost certainly because it was appalled by what it saw on the other side.

Mr Mousavi, a former revolutionary and Prime Minister, was a creature of the Establishment, not a reformer, but his candidacy threatened to unleash forces that the regime could not control. His supporters demanded detente with America and the West, greater social freedom, human rights, equality for women, an end to the hated “morality police”. Women danced in squares without the hijab (headscarf). They mocked the Government, chanting “death to the dictator” and “death to the Government”.

The wave of insurrection was rapidly becoming a tsunami, a direct challenge to the regime and its most sacred values - self-preservation. The totalitarian “deep state” took fright, and hit back in what one independent analyst described as a “coup against a coup”.

What now? Mr Mousavi continues to issue defiant statements from wherever he is hiding, and it is possible that the protests and unrest will persist. But much more likely, they will be crushed, just as the last big civil disturbances - the student protests of 1999 - were. Mr Mousavi's supporters are educated, urban, intellectual. A lot are women. They are not natural streetfighters.

Analysts argue that Mr Mousavi and his most prominent backer, the former President, Hashemi Rafsanjani, are creatures of the regime and their priority would almost certainly be to preserve it.

On the surface everything will gradually revert to the status quo ante, but below the surface a lot will have changed. Millions more Iranians will now seriously question the legitimacy of the regime. Millions will feel cheated - the turnout at the next election will be a fraction of last Friday's more than 80 per cent. These people are the middle classes, the mainstay of the economy - even a police officer who detained the Times photographer quietly admitted to feeling ashamed. They are women who glimpsed a future in which they were no longer second-class citizens, and huge numbers of young Iranians.

Seventy per cent of the 70 million population are under 30, and gross economic mismanagement and international sanctions make their futures bleak. Iran is a pressure cooker, as last week's explosion of pent-up frustration showed, and that seething discontent will continue to build, with consequences that can only be guessed at.

Hopes that Iran might be ready to re-engage with the world and to respond positively to Barack Obama's offers of dialogue have been dealt a serious blow. Israel's contention that Iran's pursuit of nuclear weapons must be stopped by any means necessary has been strengthened. The chances of Iran playing a positive role in hotspots such as Iraq, Afghanistan and the Middle East have not improved.

Meanwhile, the media's ten-day visas almost all expire this week, and the regime has refused to extend them. That leaves it free to act as savagely and brutally as it needs to snuff out the last vestiges of revolt.

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