Half an hour after Ayatollah Khomeini's revolutionary charter flight from Paris took off for Tehran 20 years ago, one of his officials stood up and addressed us.

From the archive: John Simpson arrives on Ayatollah Khomeini's revolutionary flight

"We have just received information that this aircraft will be shot down by the Shah's airforce when we cross the Iranian border."

It wasn't, of course. Instead, we circled endlessly over Tehran, watching the greatest crowd in human history gather below us.

The beginning of February 1979 saw a massive upheaval in Iranian life

Once on the ground, the Ayatollah put together an extraordinary coalition of conservative clerics, secular left-wingers and moderate reformers, all of them believing implicitly in him. The Shah's last shreds of support melted away.

At dawn on 11 February, the tanks of the Imperial Guard rumbled through the streets, while an excited army of volunteers defended the barricades.

The troops soon surrendered, and up at the Shah's palace, I watched his most faithful guards, "The Immortals", strip to their underwear at the orders of the revolutionaries.

Twenty years later, the Islamic revolution is still in full control of Iran.

Things are not nearly as harsh as most people in the West imagine: Iran is much more liberal than, say, Saudi Arabia, and women play a significant part in almost every aspect of life.

But young people, especially in the cities, tend to find it boring and repressive, and the euphoria which seized almost the entire country in 1997, when Mohammed Khatemi was elected president by 86% of the vote because he was a moderate, has long since evaporated.

The euphoria of the revolution was followed by war with Iraq in which one million Iranians died

There's a kind of gridlock in Iranian politics: President Khatemi's efforts to allow the country to open up to the West are resisted with great ferocity by the conservatives.

The battle is fought out bitterly, ministry by ministry.

President Khatami has the support of public opinion, but the conservatives believe they have the Holy Koran on their side.

It has been a terrible 20 years for Iran.

An American embargo has done heavy damage to the oil industry.

Saddam Hussein of Iraq invaded Iran in 1980 and began an 8-year war which cost the lives of one million people.

Soccer fever peaked when Iran beat the USA in the 1998 World Cup

Left-wing revolutionaries carried out a campaign of bombings and assassinations, and the government replied with torture and executions.

Things have become more settled in the last decade, but there is still no consensus about the direction this complex, sophisticated country should take. The Islamic revolution is stable, but it does not feel permanent.

There must have been 150 people on Ayatollah Khomeini's flight to Tehran in 1979, most of them young and eager revolutionaries.

From the archive: Three days after the revolution, John Simpson reports on an unstable situation

Some, including the man who made the announcement about the plane being shot down, were later executed.

Others, like the future President Bani-Sadr, were driven into exile. Many were killed in the war with Iraq, or assassinated by extremists.

Less than half of us are probably still alive today. All revolutions devour their children but the Iranian revolution had a fiercer appetite than most.