Outside, protesters declaring themselves "people united to stop the war", waved placards insisting 'No blood for oil'.
But on one of the most important days in UN history, a day on which its multilateral structures would be sorely tested by America's unilateral instincts, there was a more tempered atmosphere.
In the past this room, dominated by a Norwegian mural symbolising the promise of future peace and freedom, looking over a horseshoe seating the 15 council members, has been the backdrop for dramatic debate and bitter rows.
In 1962, during the Cuban missile crisis, the US ambassador said to his Russian counterpart: "Let me ask you one simple question: do you deny that the Soviet Union has place missiles and sites in Cuba? Yes or no? Do not wait for the interpretation. Yes or no?"
"I am not in an American court of law," the Russian replied. "You will receive the answer in due course."
Just before the Gulf war, the Iraqi and Kuwaiti delegations sat at either ends of the table, often trading bitter insults.
But yesterday there was no flagrant confrontation or open dispute, forcing observers to read the runes of every sign and signifier as the key players joined the meet and greet on the chamber floor.
UN chief weapons inspector Hans Blix greeted America's UN ambassador, John Negroponte, with a smile and a discreet thumbs-up. The Iraqi ambassador did the rounds of his Arab counterparts, air-kissing cheek-to-cheek in defiant bonhomie.
With new security measures in place, no dignitary was too grand to escape the eye of the the UN's Trinidadian security guard, to whom members of the press gallery looked for crucial inside knowledge.
But if Mr Blix's report was intended to be decisive, the US had apparently already made up their minds. Before he had even entered the council meeting Mr Negroponte told reporters: "Iraq has neither come forth with a full and complete declaration of its weapons of mass destruction, nor has it been cooperating immediately and unconditionally and actively as required by resolution 1441."
After around 15 minutes of glad-handing, with most camps sticking largely to their own end of the playground, the French chairman called the meeting to order, sending delegates and observers in search of their ear pieces, flicking through myriad unfamiliar tongues until they got to their own, or at least one that they recognised.
First came Mr Blix's report, delivered with a mixture of scientific precision and linguistic contortion. "Cooperation might be said to relate to both substance and process," he said. "Iraq has decided in principle to provide cooperation on process ... A similar decision is indispensable to provide cooperation on substance."
The words were easy enough to grasp but their precise implications remained elusive. "Let me end by simply noting that [the] capability which has been built up in a short time, and which is now operating, is at the disposal of the security council."
A plea for more time or simply a statement of fact to be discarded at will or whim? If it was difficult for British analysts to decipher, spare a thought for the embattled Russian translator whose rendition was peppered with pauses.
The report by Mohammed El Baradei, head of the International Atomic Energy Agency, was more straightforward. "We have to date found no evidence that Iraq has revived its nuclear weapons programme ... our work is steadily progressing and should be allowed to run its natural course."
To the horror of the Americans and delight of the French and Germans, twice he spelt out an extended time frame in terms of "months" - not the days and weeks that hardliners had been looking for.
But if peace hung in the balance in the chamber, war had already broken out in the press room across the corridor.
A new photocopier had been bought but, apparently, not inspected. When it broke down and was declared beyond use an undignified scramble ensued for copies of the reports, followed by a mad dash to news anchors and the bashing of mobile phones.