Leading article: Egypt: a moment of hope, but also of peril

Western leaders have struggled to come to terms with the Egyptian revolution. The US Secretary of State, Hillary Clinton, began by describing Hosni Mubarak's regime as "stable". Now she is urging an "orderly transition" of power. In the House of Commons yesterday, our own Foreign Secretary, William Hague, stressed Britian's desire for "broad-based government" in Egypt. But he also made clear that diplomatic contacts with the Mubarak regime will continue.

This confusion springs from the West's longstanding and misguided policy of propping up repressive autocrats in the Middle East, including Mr Mubarak, for the sake of regional stability. Our leaders are torn between backing the Egyptian people in their fight for self-determination, and supporting a regime in which they have invested so much.

After yesterday's anti-Mubarak demonstration in Cairo, attended by hundreds of thousands of protesters drawn from all sections of Egyptian society, it is hard to see how the President can cling on. The Egyptian army announced this week that it will not fire on demonstrators, fatally weakening the regime's hand. So, after Tunisia, it now looks likely that Egypt will become the next Arab country to experience regime change from the ground up.

Other repressive dominoes in the region could topple. King Abdullah of Jordan appointed a new government yesterday in response to protests in the capital, Amman. There have been demonstrations in Yemen. The autocrats of Algeria and Saudi Arabia will be keeping a nervous eye on events.

There is something hugely invigorating about these demonstrations of mass people-power. Democratic representation of the Arab populations, after decades of repression, suddenly looks possible.

Yet there are threats too. There has been mercifully little violence in Egypt thus far, but that could soon change. The price of food in Egypt is soaring. Youth unemployment is severe. There are a lot of desperate people in the country whose behaviour cannot be predicted. In recent days, looters have taken advantage of the preoccupation of the security services. The response of ordinary Egyptians, who have formed neighbourhood protection groups, has been impressive. But citizens alone, however well organised, cannot uphold the rule of law indefinitely.

There is a danger of violence if Mr Mubarak refuses to relinquish power quickly. And there is also an ominous lack of clarity about what would follow his departure. If a power vacuum developed, the implications could be dire. Iraq-style chaos is unlikely but is by no means impossible. The existence of sectarian animosity between Egypt's Christian and Muslim communities was made clear by last month's deadly church bombing in Alexandria.

The Muslim Brotherhood, Egypt's powerful Islamist opposition movement, has kept a low profile during these demonstrations. But if the brotherhood, which has branches across the region, chooses to assert itself the consequences will be dramatic. An Iranian-style theocracy cannot be ruled out; nor can a repeat of what happened in Algeria in 1991 when free elections resulted in victory for an Islamist movement, swiftly followed by an army coup and a civil war.

This is a moment of great optimism for millions of oppressed people across the Arab world. But it would be wrong to ignore the reality that (mainly thanks to how autocratic rulers, aided by the West, have hollowed out civic society) it is also a moment of potential danger. It is a time to hope for the best, but also to prepare for the worst.