It was three years ago that American intelligence agents began picking up signs that someone was tunnelling into the side of a mountain in the desert outside the holy city of Qom.

Mahmoud Ahmadinejad was a year into his first term as Iran’s President and had just ordered the resumption of uranium enrichment, ending the two-year suspension demanded when the world first discovered the existence of Iran’s covert nuclear programme. It was Mr Ahmadinejad’s open defiance that caught the world’s attention. But only months later, the covert defiance had begun again, too.

Intelligence agents were on the lookout for a secret enrichment plant, reasoning that if UN inspectors were monitoring the known facility at Natanz, Tehran would look elsewhere to carry out its work.

Yesterday’s revelations about Iran’s secret uranium enrichment facility at Qom came after three years of intensive investigation and surveillance by the most trusted of America’s intelligence allies: Britain, France and Israel.

Much of the previous intelligence about a military dimension to Iran’s nuclear programme had failed to convince countries such as China and Russia of the need for action. The International Atomic Energy Agency (IAEA), the nuclear watchdog of the United Nations, called Western intelligence about Iranian weaponisation research compelling but inconclusive.

The Western allies kept quiet as the evidence mounted, determined not to disclose that they knew of the Qom plant until their case was watertight. The fiasco over intelligence leading to the Iraq invasion contributed greatly to their decision.

Last week, as Tehran finally woke up to the knowledge that the plant’s security had been breached, it rushed to declare its existence to the IAEA, hoping to pre-empt other reports and prove its openness and co-operation.

That image was shattered when Barack Obama, Nicholas Sarkozy and Gordon Brown got up to address the opening of the G20 summit in Pittsburgh and, standing side by side on the stage, made their revelation.

It was, Mr Brown said, clear evidence of Iran’s “serial deception”. Not only had Tehran sought to deceive the world about the Qom plant’s existence, the evidence clearly showed that it was intended for military use.

“The size and configuration of this facility is inconsistent with a peaceful programme,” Mr Brown said. “Iran is breaking rules that all nations must follow — endangering the nonproliferation regime, denying its people access to the opportunity they deserve, and threatening the stability and security of the region and the world.” Mr Sarkozy set out a strict timetable, beginning with the scheduled meeting next week in Geneva between Iran and the five permanent members of the Security Council, plus Germany, at which they have said they expect a “serious response”.

“Everything must be put on the table now,” Mr Sarkozy warned. “We cannot let the Iranian leaders gain time while the motors are running. If by December there is not an in-depth change by the Iranian leaders, sanctions will have to be taken.”

The extraordinary joint appearance — with the German Chancellor’s remote support on screen — was hastily arranged when officials learnt that Iran’s declaration to the IAEA was about to become public. Iran had given only the briefest of details in its short, cryptic note to the the IAEA, saying that it now had a “pilot plant” under construction, the existence of which had never before revealed.

Russia was briefed on the disclosures in bilateral talks with Mr Obama at the UN General Assembly in New York. The revelation appears to have brought President Medvedev of Russia round to his reluctant admission that “sometimes sanctions are inevitable”. China, however, was not trusted with the information until late Thursday. Russia released a statement yesterday saying that it was worried by the development, while China said that it had taken note of the information and urged Tehran to co-operate with an IAEA investigation. A Chinese official said that it wanted the matter to be dealt with by the IAEA.

Diplomats from the three countries briefed the IAEA in Vienna yesterday morning on their findings. Mr Obama called on the agency to demand immediate access to the plant and verify their findings. The IAEA confirmed that it had been told on Monday by Iran that “a new pilot fuel enrichment plant is under construction in the country” and said it had already requested more information and access as soon as possible. “The agency also understands from Iran that no nuclear material has been introduced into the facility,” the statement said.

The IAEA officials were not the only ones who appeared blindsided by the public revelation. Mr Ahmadinejad learnt of the impending announcement at a breakfast interview with Time magazine editors in New York yesterday morning. Footage posted on the magazine’s website captures the moment he is told of what the three leaders are about to do.

Mr Ahmadinejad’s face appears to freeze, his eyes glide slowly around the room and he checks to see that the statement has been translated correctly before attempting to answer. “If I were Obama’s adviser, I would definitely advise him to refrain from making this statement because it is definitely a mistake,” Mr Ahmadinejad said.

He went on, his answers ranging from the defensive to the aggressive. “We have no secrecy, we work within the framework of the IAEA,” he said. “This does not mean we must inform Mr Obama’s Administration of every facility that we have.” The announcement “simply adds to the list of issues to which the United States owes the Iranian nation an apology over”.

After he had time to compose his thoughts, Mr Ahmadinejad remained defiant. He said that because the site would not be up and running for 18 months, and IAEA rules required it to be informed of any new enrichment facility six months before it became operational, Iran had broken no rules. With an eye on the forthcoming talks with the West he said that Mr Obama would regret yesterday’s statements.

Qom: a holy city

One of the holy cities of Shia Islam and the world’s biggest centre for Shia scholarship, with a population of about one million

On the banks of the Rud-e-Qom river and beside a salt desert

Site of the shrine of Fatema Maesume, the sister of Imam Ali ibn Musa Rida (AD789-816), one of the 12 Imams who succeeded the prophet Muhammad in Shia Islam. Became a pilgrimage destination in the 17th century

Home to Iran’s largest theological university; about 50,000 scholars from 70 countries work and study in the city Iran’s conservative clerics are based here, but it has a long history of dissent and was the centre of campaigns against Russia and British colonial power in the early 20th century

Ayatollah Khomeini planned the Islamic Revolution of 1979 in Qom

Renowned for its architecture including mosques, golden minarets, shrines and tombs

Sources: Encyclopaedia Britannica, Times database

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