By Gordon Corera
BBC security correspondent
It was just before midday on 17 February in 2003 when the quiet of a suburban street in Milan was momentarily disturbed.
Extraordinary rendition is now part of the CIA's tactics
The bearded man in a tunic was walking down Via Guerzoni when he was approached by two men speaking Italian. One asked for his papers.
Once they confirmed his identity, he was bundled into a white van.
This was a so-called extraordinary rendition - a term referring to the abduction of terrorist suspects and their removal to countries other than the US for imprisonment and interrogation.
The man taken was a radical Egyptian cleric Abu Omar. Those thought to be responsible, the CIA.
Abu Omar was believed to have been flown from an American airbase at Aviano in Italy, to Germany and then on to Egypt.
In 2004, he was briefly released, and phoned his relatives and friends back home.
A friend with whom Abu Omar was in contact later gave a statement to the police in which he claims the cleric was subjected to torture.
"The first measure was to leave him in a room where incredibly loud and unbearable noise was made. He has experienced damage to his hearing," he said.
"The second torture was to place him in a sauna at tremendous temperatures and straight after to put him in a cold storeroom, occasioning terrible pain to his bones... as if they were cracking.
"The third was to hang him upside down and apply live wires to the sensitive parts of the body including his genitals... and producing electric shocks."
What is remarkable about this case is how public it has become.
Italian prosecutors have opened up a case and issued arrest warrants for 22 alleged CIA operatives involved.
The prosecutors have amassed a wealth of detail, including phone calls from the scene of the kidnapping, car registration details, even their hotel bills for their time working on the operation (one individual managed to run up a $9,150 bill for three weeks at one of Milan's top hotels).
One alleged CIA operative amassed a large hotel bill
Armando Spataro, Milan's deputy chief prosecutor and the city's counter-terrorist co-ordinator, says the kidnapping was not only a serious crime against personal liberty and Italian sovereignty, but has also done serious damage to the fight against terrorism.
Police in Milan were already on to a group around Abu Omar and later made arrests.
"If Abu Omar was not kidnapped, we could have arrested other people," says Mr Spataro.
"We could have discovered other illegal links... This kidnapping was also very dangerous because it pushed [the] Islamic moderate part of the community to become extremists."
So far, prosecutors have found no evidence that the Italian authorities knew of the kidnapping, but not everyone is so sure that they were in the dark.
Question of timing?
European governments have protested their ignorance, but retired CIA officer Mike Scheuer thinks this is plain hypocritical, and that the apparent sloppiness of those involved in the Abu Omar case is, in fact, a sign of something else.
"What's been described about hotel reservations and the use of telephones doesn't make sense if you're going to be running an operation unilaterally without the host government knowing.
"Clearly, the Italians were co-operating. But more than that, that operation was aimed at a very mid-level middling Islamist, no-one that we would bother with off our own hook.
Mr Scheuer believes Italy co-operated with the CIA
"But the more important issue was it occurred on the eve of the war in Iraq. The Italians, along with the British, were about the only Europeans standing with us.
"If you think any American government would have the courage in that situation to conduct a unilateral operation in Italy, then you know nothing about the US government."
Other sources in Washington also indicate that they believe parts of the Italian government would have known about such an operation. However, the Italian government has denied this.
Despite their professions of ignorance and outrage, almost all European governments are now facing questions about how much they have known about CIA operations.
Have they been turning a blind eye? Have they allowed European airspace to be used for rendition?
There is a suspicion in some quarters that they co-operate in secret but back off fast when CIA operations become public.
Others believe that governments simply choose not to ask too many questions about what may be going on, even when it involves their territory.
Whatever the case, the CIA's increasingly toxic reputation in Europe is causing some serious headaches, and may be making vital co-operation in the war against terrorism even harder to maintain.
This edition of Secret Wars by Gordon Corera was broadcast on BBC World Service on Monday 20 March.