The conclusion of the United Nations nuclear watchdog (IAEA) after visiting Libya last week was that Colonel Muammar Gaddafi was "some years away" from a nuclear weapon. Reassuring - but possibly mistaken.
British and American officials who have made secret visits to Libya's weapons laboratories found instead that Colonel Gaddafi was "well on his way" to making a nuclear bomb.
ElBaradei said Libya's nuclear equipment was "still in boxes"
If they are right, Libya posed a far more serious threat than that detected by UN inspection teams just allowed into the country.
"We saw uranium enrichment going ahead," said one senior diplomat with knowledge of the Anglo-American inspections. "We were satisfied that they were well on the way to developing a weapon."
The official added: "Libya was third on our list of concern after North Korea and Iran."
'At early stage'
The head of IAEA, Mohammed ElBaradei, said his UN team had found nuclear equipment "still in boxes".
"They were still a few years away from developing a nuclear weapon," Mr ElBaradei said. "This is a programme at an early stage of development."
"They have not enriched any uranium to our knowledge. They have not built any industrial scale facility, it was all at the pilot, laboratory scale," he added.
The IAEA inspectors were taken to four sites near Tripoli over the course of a single day.
The British and American experts saw much more, spending three weeks in Libya during two visits in October and then in December.
Colonel Gaddafi wants international rehabilitation
The western diplomat we spoke to was confident that Libya would in time reveal to the IAEA inspectors the full extent of its clandestine effort to a nuclear bomb.
"At first, there were quite a lot of moments when we felt they were not being fully frank. But trust has grown," the diplomat said.
He went on: "This was a decision some time in the making. Some years ago, Colonel Gaddafi realised he was taking Libya the wrong way."
The reassessment is said to have picked up speed after the 11 September attacks - and especially since Iraq was invaded.
The secret diplomacy which led to the breakthrough began back in March with an approach from the Libyans just as American and British tanks were about to roll into Iraq.
The diplomat said that the way was now open for a visit to Libya by UK Prime Minister Tony Blair.
Tony Blair said he applauded Libya's move
"Gaddafi is a mercurial person and many times in the past he's gone back on decisions on a whim or because of some perceived slight," the diplomat said.
"We need to lock Libya into this virtuous circle. A visit here by Tony Blair is the best possible means to secure this," he added.
The IAEA, too, will now return to Libya to mount a series of snap inspections under a new protocol agreed with the Gaddafi regime.
"We still have to do a lot of work," said Dr ElBaradei.
"We still have to interview people, get access to information, and once we understand the full nature of the programme then we will have to see how to render that programme harmless or neutralise it."
Hunt for Libya's supplier
Even in his single day of inspections, Dr ElBaradei said he had found breaches of Libya's international obligations.
"There were some imports that they should have declared to us," he said, "and activities that they should have declared to us."
The lessons of the Libyan experience was that "export control has not been working. We clearly need much more stringent verification regime".
The hunt is now on for Libya's supplier. British and American concern is focussed on an unnamed third country which supplied both Libya and Iran - possibly North Korea.