It was the pivotal moment of the most famous political interview of the century; David Frost, the son of a minister from Beccles in Suffolk, threw down his challenge to the recently deposed leader of the Western world by taking his clipboard of questions from off his lap and tossing it to the floor.
The symbolism of this theatrical act was immediately clear to an audience of more then 45 million Americans, that the formalities were over, that the quasi-judicial nature of the many hours of interview that had gone before could now be dispensed with. No more thrust and parry, and no more prosecutor and defendant. It was time for Richard Nixon to come clean.
As he remembers it now, Sir David Frost describes this career-defining point as "the most heart-stopping moment". Under constant probing from Frost, the former president, giving his first interview since his resignation over the Watergate scandal in 1974, had started to crumble. And when Frost told him "mistakes" did not seem an adequate enough description of the former president's wrongdoing, Nixon asked him: "Well, what word would you express?"
"I sensed he was more vulnerable than he might ever be again," says Sir David. "I thought I better really lay this out fully. So I threw my clipboard aside to indicate we were going into territory that neither of us had necessarily planned."
That clipboard represented so much. This was one of the most ambitious projects in television history, masterminded by a British journalist determined to create a chapter of American history. Frost had personally persuaded Nixon to do the interview and had himself raised the finances, including the former president's fee of $600,000. The clipboard was the result of months of assiduous research by his hand-picked team, and part of his carefully prepared strategy for a game of cat and mouse that stretched over 28 and three-quarter hours of filming. Now Frost told Nixon what to say. "I told him I felt he should say there had been wrongdoing, that he had let down his oath of office and he should apologise that he had put the American people through two years of needless pain."
Over the next 20 minutes, Nixon, rather like a suspect in an interrogation room who realises the game is up, did just as Frost had instructed. The culmination of this mea culpa provided some of the most dramatic moments on television. "I let down my friends," said Nixon. "I let down the country. I let down our system of government and the dreams of all those young people that ought to get into government but think it's all too corrupt. I let the American people down and I have to carry that burden with me for the rest of my life. My political life is over."
After so many hours of probing, it was time for Frost to sit back and listen. "The drama of it was incredible and we were both, I think, drained by the end of that two-and-a-half-hour session."
For Nixon, the admission would at least mean the start of his gradual rehabilitation into American society, so that his achievements were not entirely overshadowed by Watergate, The Washington Post's revelation of White House involvement in the bugging of the offices of the Democratic National Committee, a story portrayed in the 1976 film All the President's Men, starring Robert Redford and Dustin Hoffman. For Frost, the 1977 broadcast of the first interviews with the disgraced president catapulted him to being seen as the world's most famous political interviewer.
This was a television programme on a scale we could hardly imagine today. Frost was not the ingénue suggested by Peter Morgan's acclaimed new feature film, having already interviewed Nixon in 1968 prior to his election as president. But it was something else to persuade America's first president to resign that he should break his silence to a lone British television journalist, rather than the giant NBC network. Frost's breakthrough came when Nixon's colourful new publicist Irving "Swifty" Lazar decided a television interview could help the former president recover credibility.
By offering $600,000 for four 90-minute shows, Frost outbid NBC but then realised no American network would take his independently produced programmes. Undaunted, he created an alternative platform by teaming up with the distribution company Sindicast and an alliance of 200 small stations across America. Then he had to find the money. James Goldsmith, Polygram and the Australian media magnate Kerry Packer all helped but Frost finalised the funding only after the interviews started.
The Frost/Nixon interviews, though they appear to be fought mano-a-mano (an "intellectual Rocky" as Morgan describes his film), were in fact a battle between two teams. Frost was driven forward by John Birt who took leave from London Weekend Television to work on the project. Birt would later became an austere director general of the BBC but was then a young man with hair to his shoulders, described by Frost as "the most outstanding current affairs producer I had ever worked with".
Three more journalists were recruited, headed by Bob Zelnick, an experienced American public radio reporter who had grown up in the Bronx and had practised as a lawyer. On Nixon's side was a collection of Republican heavyweights, including close adviser Jim Brennan and Ken Khachigian, who would later become a speechwriter for Ronald Reagan, and Diane Sawyer, a future star of ABC News.
The Frost team trawled through the Watergate evidence and uncovered previously unreported tape recordings that further implicated Nixon in Watergate. They then moved to the Beverly Hills Hilton, where they planned their strategy for the 12 days of interviews in a private house near Nixon's home in San Clemente. Mr Zelnick, now chairman of the Department of Journalism at Boston University, Massachusetts, says he wanted the interviews to be conducted as if they were legal proceedings. "I said we have to make this the trial that Nixon never had."
Nixon's team was informed of the subject matter of each stage of the interviews, though not the actual questions, so he could respond properly. Yet after all the preparation, the interviews – on the Vietnam war, the Huston plan to counter political violence within America and Nixon's relationship with former secretary of state Henry Kissinger, as well as Watergate – got off on the wrong foot. In the first session on Vietnam, Frost opened up with: "Why didn't you burn the tapes?" Mr Zelnick recalls Nixon's response. "He thought we were screwing him." The former president became evasive. In Mr Birt's autobiography The Harder Path, he writes, "We feared that David was not taking control and was not driving the interviews hard enough". On the eve of filming, Mr Birt had slipped a hand-written note under Frost's door, urging him to "keep up the pressure at all times: you will win only if you can, so to speak, sprint the mile".
By the time of the Watergate interviews, Frost was at full speed, at one point reciting rapid-fire 16 of Nixon's most damning quotes and, through his intricate knowledge of the detail, forcing the former president to admit he had been responsible for the obstruction of justice. Two days later, Frost arrived for the final Watergate session, but Nixon arrived 17 minutes late. "He had that haunted look that he had at the time of the actual Watergate sessions as if he'd been reliving them in those two days."
More than three decades later those events are still fascinating. "It would have been impossible to predict that it would be so relevant and so public 30 years later," says Frost. "And I guess it will stay that way because Nixon died, so he can never give another interview."