By John Simpson
BBC World Affairs Editor
John Simpson reporting from Tehran before his visa ran out on Sunday
For reasons best not explained, I've come to know a former member of the Revolutionary Guards really well.
He's done some pretty dreadful things in his life, from attacking women in the streets for not wearing the full Islamic gear to fighting alongside Islamic revolutionaries in countries abroad.
And yet now, in the tumult that has gripped Iran since its elections last week, he's had a change of heart.
He's become a backer of Mir Hossein Mousavi, the reformist candidate who alleges fraud in the elections. He's saved up the money to send his son to a private school abroad, and he loathes President Ahmadinejad.
He's not the only one.
I had to leave Iran last Sunday, when the authorities refused to renew my visa. But before I left, another former senior Revolutionary Guard came to our hotel to see us.
"Remember me," he pleaded. "Remember that I helped the BBC."
I realised that even a person so intimately linked to the Islamic Revolution thinks that something will soon change in Iran.
The 11 extraordinary days I spent there was my 20th visit in 30 years. I've been reviewing the material we recorded, taking a second look at what was really going on.
I think that these last weeks may turn out to be as momentous as the Islamic Revolution I witnessed there 30 years ago.
The Revolutionary Guards with second thoughts illustrate some of the deeper forces driving a crisis which I believe could change Iran forever.
The first big change is that nowadays in Iran, even when you meet an official you can't necessarily tell which side they're on.
It's as if the fabric of the Islamic Revolution itself has been torn; so much so that individual government ministers, civil servants, Republican Guards, senior military men, and all sorts of others, have taken sides, reflecting a power struggle at the very top.
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BBC Radio 4, Thursday 25 June, 2000 BST
You can see this reflected on the streets in all sorts of ways. In the protests, for example, where the crowds were bold enough to protect our BBC team from secret policemen.
Driving around Tehran gathering TV material, we often found ourselves in difficult situations as authorities clashed with crowds of protesters chanting slogans like: "We want freedom."
In one memorable incident, a group of street demonstrators actually chased away a man in plain clothes from the once-feared state security.
They felt brave enough to do it because they know that many within the state system itself are actually backing Mr Mousavi and the protests.
After we were ordered to leave Iran, we went around to the Ershad, the Islamic Guidance Ministry, which supervises foreign journalists.
We expected to be scolded and intimidated. But, in fact, the body language of the person who spoke with us was bizarrely apologetic.
The official said we could stay in the country a little longer and "do our shopping" - a code for our work.
This was accompanied simply by a warning not to get arrested by the police.
It illustrates the split that goes all the way through Iranian society.
It's not just about President Ahmedinejad and his challenger Mir Hossein Mousavi.
It's about two much bigger characters, locked in a confrontation that the rest of the crisis reflects.
On one side is Ayatollah Khameinei, the arch conservative who keeps the Islamic revolution together. On the other, a cynical figure who has made a pile of money since the revolution: former President Ali Akbar Rafsanjani.
Mr Rafsanjani is one of the few people in Iran who could stand in open opposition to the Supreme Leader because, as his friends are fond of claiming, he first installed Ayatollah Khamenei - who wasn't considered a particularly distinguished theologian at the time.
Rafsanjani has dominated Iranian politics since the 1980s
For almost a decade, this worked to both men's advantage.
Then in 2005, Mr Rafsanjani made the disastrous mistake of standing for the presidency a third time. His former protege was by now powerful enough to turn against him.
The public were sick of the corruption they associated with Mr Rafsanjani. They stayed away from the polls in droves, handing victory to the Supreme Leader's new favoured candidate Mahmoud Ahmedinajad.
I first encountered Rafsanjani during the Iran-Iraq war, and I must confess I liked him.
He's very amusing and charming, though I wouldn't like to have him as my enemy.
I remember one press conference from the mid-80s where, as usual, the women sat separately from the men. In those days women journalists were almost exclusively right-on hardliners, very earnest and dressed in the deepest black.
Mr Rafsanjani came to the microphone, looked at them irritably for a moment or two, and asked, "Can anyone tell me where it says in the Holy Koran that women have to make themselves look ugly?"
But that doesn't make him a liberal. In fact, Mr Rafsanjani remains every inch a man of the Islamic Revolution.
Today he operates from the shadows using the wealth he has amassed, rather like a Russian oligarch.
But while the idealistic young people rally behind the slogan: "Death to the Dictator," I am not fully convinced that a Rafsanjani Iran necessarily offers the more open form of government they are risking their lives for.
Both sides in this struggle are strong believers in the Islamic Republic.
It may change, but it isn't finished. And the great mass of people who've taken part in the demonstrations could find themselves just looking on from the outside, as they did before.
The Report with John Simpson is on BBC Radio 4, Thursday 25 June at 2000 BST. You can also listen via the BBC
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