Nor was it even the relatives of the victims on that day in 2001, who told their heartbreaking stories, nor the brave passengers of United Airlines flight 93, whose uprising against the hijackers was preserved in the cockpit recording played publicly for the first time during the trial's final penalty stage.

Nor was it even the jury that gave the lie to the world's image of America as a country that sees capital punishment as the solution to every crime.

No, the hero, or rather the heroine, was an elderly woman, barely five foot two inches tall, her greying hair pulled back into a matronly bun, peering out over spectacles halfway down her nose. Leonie Brinkema was the federal judge whose lot was to conduct one of the most high-profile and sensitive trials in the US in recent times, watched around the world, and featuring a defendant determined to turn the event into a theatre show for himself and his cause.

Never, even when facing the direst provocation, did she lose control of proceedings. And when everything was finally over on Thursday . . .as she formally sentenced Moussaoui to the term of life in jail without parole the previous day . . . she found the perfect words.

"You came here to be a martyr and to die in a big bang of glory, " she told the 38-year-old FrenchMoroccan terrorist, who pleaded guilty in 2005 to conspiring with al-Qaeda in the attacks which killed 3,000 people. "But to paraphrase the poet TS Eliot, you will die with a whimper."

Whimper is not a word one would associate with Moussaoui, whose erratic outbursts and brazen histrionics have driven even his own defence team to distraction. But 'whimper' is an exaggeration when applied to what will be heard from Moussaoui for the rest of his natural life.

By the time you read this, he will probably already have been transferred to the bleakest, most secure federal prison in the US, the 'Supermax' penitentiary near Florence, Colorado, known as the Alcatraz of the Rockies. In the words of his mother, this is where Moussaoui will be "buried alive". He will join some of the country's most famous convicted criminals, among them the 'Unabomber' Ted Kaczynski, and Terry Nichols, the accomplice of Timothy McVeigh in the 1995 Oklahoma bombing that until 2001 was the deadliest terrorist act on US soil.

Richard Reid, the British-born 'shoe bomber', is there, as is Robert Hanssen, the high ranking FBI official who spied for Russia for 15 years, and Ramzi Yousef, who plotted the 1993 attack on the World Trade Centre. But Moussaoui will see little of them. He will spend 23 hours a day in a concrete cell measuring seven feet by 11. It has a concrete bed, an immovable concrete stool and desk, and a small black-and-white TV carrying a few selected channels, classes and religious services. A four-inch window offers a view on an inner courtyard.

For the first years at least, he will have no contact with fellow prisoners. His only visitors will be his lawyers. Each time he is allowed out of his cell, it will be in shackles. And so it will be for ever, under a life sentence without possibility of parole that is perhaps even worse than death.

Many Americans will view the outcome with mixed feelings. The overwhelming expectation had been that Moussaoui would be sentenced to die, especially after he had bragged of being a key participant in the conspiracy, and jeered at the prosecution witnesses, including the relatives of the victims who were in tears as they described their loss.

But in their 41 hours of deliberations, the jurors found mitigating factors . . . some surprising, others less so. Three jurors for instance, reasonably insisted that Moussaoui's role in the plot was minimal. Perhaps less predictably, nine of them attached importance to his dysfunctional childhood, scarred by abuse from his father and a lack of emotional support from his mother.

It was an astonishingly rational end to what had often seemed a most irrational case. Was Moussaoui a sane man pretending to be mad to escape execution? Or was he genuinely mad? Or were his antics meant to secure him the death penalty, and thus an entry in the book of martyrs for his perverted Islamic faith? The answer may never be known.

Most important of all, Judge Brinkema proved the system can work. "America, you have lost, " Moussaoui sneered in his final appearance, gloating at the prosecutors' failure to win a death sentence. In fact America achieved a precious victory.

Several times proceedings neared collapse . . .

over Moussaoui's insistence on defending himself, over whether captured suspects could be called as witnesses, over crass mistakes by the prosecution, over his rantings, and over his wilful selfincrimination when he claimed he and Reid were on a mission to fly a plane into the White House.

But, steered by Brinkema, justice held firm.

For the Bush administration, however, this victory could be awkward. The Moussaoui case has proved that, contrary to government claims, terrorist suspects can have a fair trial in a normal US court. This raises yet more questions about Guantanamo Bay, and the entire pursuit of those responsible for the 2001 attacks. How can the wretched inmates at Guantanamo . . . some of them far less significant than Moussaoui yet held for over four years . . . be denied their own day in court in the US?

So far only 10 of the 500-odd inmates there have even been charged with anything.

Then there are the wider repercussions for Bush's war on terror. It may well be that Zacarias Moussaoui, a relative minnow, turns out to be the only person tried in connection with 9/11. But why? True, the 19 hijackers who carried out the attacks died on the day. Other members of alQaeda high command who helped arrange it have been killed. But others, including Khalid Shelk Mohammed, the purported mastermind of the operation, have been captured.

By now these people have surely been drained of all relevant intelligence. Will they simply rot in unknown CIA jails and detention centres? Could they not be given some form of public trial, so that Americans can learn more of the truth about what happened that day? Then, assuming they are convicted, they could either be sentenced to death or, like Moussaoui, spend the rest of their days in the Alcatraz of the Rockies.