That close encounter was finally ended on Tuesday, exactly three months after the start of a libel trial initiated by Irving.
Addressing a packed High Court in London, Justice Charles Gray ruled that Lipstadt had proved the central charges she had laid against Irving in her 1994 book, "Denying the Holocaust: The Growing Assault on Truth and Memory." Also exonerated was Lipstadt's British publisher, Penguin UK.
Gray, the quintessence of British correctness, courtesy and understatement, did not mince words when he declared that Irving was indeed, as Lipstadt had charged, an anti-Semite, a racist, a distorter of history, a partisan of Hitler and a Holocaust denier.
Referring to Irving's political activities, the judge said "the content of his speeches and interviews often display a distinctly pro-Nazi and anti-Jewish bias."
"He makes surprising and often unfounded assertions about the Nazi regime which tend to exonerate the Nazis for the appalling atrocities they inflicted on the Jews.
"The picture of Irving that emerges," said the judge, "reveal him to be a right-wing pro-Nazi polemicist."
He found that "for the most part, the falsification of the historical record was deliberate... Irving was motivated by a desire to present events in a manner consistent with his own ideological beliefs, even if that involved distortion and manipulation of historical evidence."
He ruled that Lipstadt had failed to prove that Irving has a self-portrait of Hitler above his desk, that he was scheduled to speak at an anti-Zionist conference in Sweden which was to have featured neo-Nazis and representatives of Hamas and Hezbollah and that he had exposed parts of the original Goebbels diary to potential damage.
But he added that, in light of the charges which had been proved, the unproved charges would not have "any material effect on Irving's reputation."
Irving, who lives in a $1.5 million apartment in London's smart Mayfair district but says he has no other assets, now faces a bill for legal costs estimated at some $5 million. He also faces public humiliation and bankruptcy.
For Lipstadt, the judgment brought a moment of "intense joy and deep gratitude that I had people around me who helped me get through this ordeal."
At the same time, however, she expressed sorrow that Holocaust survivors who had attended the trial were compelled to endure Irving's courtroom taunts.
She came close to tears when she recalled being "enveloped by survivors" who had approached her during the hearings to thank her for her stand against Irving.
But even as her ordeal was ending, she warned: "The nightmare is not over. There is no end to the battle against racism, anti-Semitism and fascism."
The trial, she said, had been "a long and difficult process" and she hoped that "this victory will save other authors from having to face such trials and tribulations."
"I see this not only as a personal victory but also as a victory for all those who speak out against hate and prejudice."
In court for the judgment, as on each of the 32 days of the trial, Lipstadt and Irving were in a state of active confrontation and conflict. But at no point did they either lock eyes or exchange words.
There was, however, one important difference in the mien of the protagonists on judgment day: While Lipstadt maintained her well-tailored, dignified calm, Irving was a broken man.
He knew already, when he charged into court just one minute before the scheduled start, that he had lost. Gone was the imperious arrogance, the scorn and the contempt which had defined both his style and his substance since the trial opened.
Gone, too, was the trademark "English gentleman" pinstriped jacket. All that was visible from the press gallery behind him was the shirt on his back. And that, he must know, might soon be gone, too.
Still, Lipstadt could not bring herself to express sympathy for a man who had consumed so much of the past five years of her life with his bile, who had vilified the survivors and "danced on the graves" of the victims.
The contest was an almost classic encounter between the forces of light and the forces of darkness, a case that could have been subtitled Beauty and the Beast: the trial of a soft-spoken Emory University professor dragged before the High Court in London to answer charges of libel by a brutish right-wing extremist.
Typically, when I met Deborah Lipstadt the day before, preparations for Pesach were as much on her mind as the looming verdict.
She had just arrived back in London from her home in Atlanta, Georgia, where she had spent 10 days cleaning for Pesach and preparing for the annual influx of family for her second seder. "Half of my Pesach is cooked and in the freezer," she announced proudly.
Nor was the message of the holiday lost on this doughty fighter: "Here we are on the eve of Pesach, and what is Pesach all about: To teach your children."
That, in essence, was how she perceived the significance of the legal ordeal she has endured.
Borrowing from the Haggadah, which will be used in millions of Jewish homes next week to retell the story of the exodus from Egypt, Lipstadt declared that "if, in the future, I can use this experience to teach and to write more history, then, in the spirit of the approaching holiday, dayeinu -- it will be enough for me."
While she had set out in her book to demolish the Holocaust revisionists who pump poison into the bloodstream of academic and public debate, Lipstadt was not looking for a fight.
"But once it came within the parameters of my life, there was only one way I knew how to respond -- and that was to fight back."
She did not seek a court battle that would overwhelm her professional and personal life: "I never would have gone into court with these people -- I don't think it's productive," she said. "But once they came after me, I had no option but to fight with all my strength and with all my might."
Caught in the spotlight of a case that attracted standing-room-only public galleries and the constant glare of international media attention, Lipstadt maintained an internal tranquility by methodically ordering her time.
Days were spent in the courtroom; evenings at her apartment in London's West End, which was, ironically, just a few minutes walk from Irving's home.
"I'd come back to my apartment and generally change into exercise clothes. Sometimes I'd go and work out, then I'd answer e-mails, read transcripts, go over material that was going to be covered next day in the case.
"In the early part of the evening would come calls from every place east of here -- friends in Europe and Israel. Later would come calls from west of here. Then I would go to sleep. It was all very routine."
There were few emotional roller coasters, but she admitted that "a couple of times, when real ugliness came out in the court, it was revolting. I just wanted to go home and take a shower."
What kept her strong was what she described as her "A-Team" of lawyers, paralegals, researchers and experts, who, she said, would have been the toast of any university history department. "The fact they were all working so hard, that they were so dedicated, was a source of support in and of itself."
Then there was the flood of e-mails, letters, notes, cards and phone calls she received from well-wishers around the world -- "Jews and non-Jews, people I know and people I don't, scholars and nonscholars, taxi drivers and hotel concierges, wanting to do things for me, wanting to be there, to help me."
But most moving and most touching, she said, was "the recognition by so many people -- again, Jews and non-Jews -- that while I was the person on the front line, this was not my struggle alone; that it really was a struggle for truth, for memory, for doing the right thing."
Her contempt for Irving was boundless: "He is a liar and he is a bully," she said almost matter-of-factly, almost recklessly, considering she did not then know the verdict of the court.
"To manipulate the historical record in such a contemptuous fashion and to take what appeared to me to be such glee in making fun of survivors -- that was debilitating. But the effect was to make me even more convinced I was doing the right thing."
Did she now regret anything in the book? "Yes," she replies vehemently. "I regret that I didn't know then what I know now, because then I would have been much more severe in what I wrote about Irving."
With the benefit of hindsight, would she have written the book at all? "Without a doubt," she said emphatically, stressing each syllable. "To say I wouldn't have written it would be to give succor to scoundrels."
The trial has transformed Lipstadt-the-academic into Lipstadt-the-celebrity. But she will not be cashing in on her new status.
Deborah Lipstadt's dream is to return to her university, which has stood by her steadfastly, and pick up where she left off before the start of the legal proceedings.
"I hope," she says, "that I can use this experience in what I do professionally -- in what I do best and what my life has been all about: To teach, to teach, to teach."