Wikileaks opens window on the Middle East thinking
Anyone who has spent time researching in government archives, rifling through boxes of diplomatic telegrams, will recognise the tone in the documents that have come from Wikileaks.
Diplomats back in their embassies are writing up accounts of meetings, adding analysis of their own and pen portraits of the people to whom they have been talking.
Sometimes it is not much more than colour, high quality gossip - useful stuff but an illumination rather than a revelation or a record.
But sometimes they are relaying direct quotes from national leaders, or from their close advisers.
The difference between the Wikileaks material and the files of yellowing paper in the archives is time.
Usually historians have to wait a generation, at least, before they get to see the written diplomatic record.
Now we are all able to get a taste of the conversations that are going on, right now, inside palaces and foreign ministries about the big issues of our time.
Anybody who follows the smouldering crisis over Iran and its nuclear ambitions over the last few years will have been working things out for themselves.
Before this huge leak of classified American documents they would have been able to tell you, for example, that Iran's neighbours in the Gulf were deeply worried about Iran, and scared about what it might do.
They would have heard predictions of a nuclear arms race if Iran developed a bomb, something, by the way, that the Iranians deny repeatedly that they are doing.
And they would have heard endless speculation about the chances of an American or Israeli attack on Iran's nuclear sites.
But what is different now is that we have seen the Saudi ambassador in Washington reminding senior Americans that when it comes to Iran, King Abdullah has told them "to cut off the head of the snake".
We can read King Hamad of Bahrain's opinion on Iran's nuclear programme that "the danger of letting it go on is greater than the danger of stopping it".
And, in case you thought diplomatic exchanges were straightforward, here is the Prime Minister of Qatar, Sheikh Hamad Bin Jassim al-Thani talking about the way his country does business with Iran: "They lie to us, and we lie to them."
I knew that the Sunni leaders of the Gulf Arabs were suspicious, not to say paranoid, about Iran.
But it was a remarkable to see just how deep that goes, and how vehemently some of them have argued for the Americans to attack Iran.
Window on thinking
For reporters who spend far too much time outside important buildings trying to find out what is being said inside them, it is fascinating reading.
But will the airing of what was supposed to be secret change anything?
After all, the people quoted in the cables, and the diplomats who passed on their views, know what was said.
US foreign policy will not be changed. America's allies in the Gulf and in Israel are not going to alter their views of Iran.
But the subjects of the powerful and largely unaccountable leaders of Arab countries now have a window on their thinking.
They are not used to getting unvarnished quotations of the private thoughts of their rulers, and they may not like what they hear.
Iran creates nervous tension in the minds of the leaders of Saudi Arabia, Egypt, Jordan and the rest not simply because it might be trying to make a nuclear weapon.
Shia Muslim Iran and its allies, notably Hezbollah in Lebanon, have shown that they can enthuse Sunni Arabs in ways that their own leaders cannot.
In the Arab Middle East one of the critical tests of political virility, a sure way for a leader to get a crowd on his side, is stand up to Israel and its western allies.
How will Iran react?
But these days it is complicated. The autocratic leaders of the Saudis, Jordanians and Egyptians depend on American military and political support. Jordan and Egypt have peace treaties with Israel that are not popular at home. Iran does not have any of those constraints.
Sunni Arab kings and presidents have uncomfortable memories of the way that Iran's ally Hezbollah, and its leader Hassan Nasrallah, seized the imagination of their own people when they fought Israel to a standstill in 2006.
Now their own people can see that in private they are saying the same things about Iran as many Israelis and neo-conservative Americans.
The biggest questionmark is over Iran's reaction.
In public President Mahmoud Ahmedinejad has been dismissive about what was said in the cables.
There may be some more clues in the talks due for next week between Iran and the permanent members of the UN Security Council plus Germany, assuming they go ahead.
Iran may be more concerned at the moment about the assassination of one of its nuclear scientists and an attempt on the life of another.
A widespread assumption, voiced too by President Ahmedinejad, is that Israel and the West were behind the attacks, though some analysts say they were another sign of the turmoil inside Iran.
The point is that it is hard to tell. The Wikileaks material shows that the United States, which does not have an embassy in Tehran, finds it difficult to work out what is happening in Iran.
One of the leaked cables from 2007 has the then British ambassador in Tehran, Geoffrey Adams, coaching the US General David Petraeus and the US ambassador to Iraq about how to negotiate with the Iranians.
His advice was to be tough, not aggressive, keep the message clear, and don't be too subtle.
One point is worth holding on to for those who believe that an attack on Iran would have catastrophic consequences.
It has been clear for some time that Israel and its supporters in Washington DC would like the American military to attack the Iranian nuclear programme. Now we know that the pressure has been coming from Arabs too.
And the US has chosen not to take the advice of any of them.