Nevertheless, the Kentuckian was far from assured championship glory, since he soon came back under attack from Capirossi - who retook second on lap eight - meaning that Rossi now only needed eighth place. Retirements ahead had raised 'Vale' to 14th by lap 12, but it was already clear that, for whatever reason, the Italian didn't posses the speed needed to reclaim the title.
Rossi's fastest lap of the race, set before his fall, was only seventh best and by the halfway stage the #46 still had over 13 seconds of open asphalt between himself and 13th placed Makoto Tamada. It was a gap he simply couldn't bridge and Rossi's only chance was a Hayden mistake.
Nicky's pit board had immediately informed him of Rossi's downfall and as the race entered its closing stages he was reminded that third position was 'ok' since, combined with Rossi's 13th place, he would take his first world title by five points. The faultless former AMA Superbike champion thus settled into a safe pace that left him equidistant between second placed Capirossi and fourth placed Pedrosa right to the chequered flag, which he crossed slumped on the tank as the shock, emotion and excitement of achieving a lifelong dream was released. It was also Honda's first title since Rossi left the team at the end of 2003.
To put Hayden's amazing achievement into perspective, he had become only the second rider ever to come from behind and win the title at the final race - and on the only previous occasion, in 1992, Wayne Rainey had been just two points behind Mick Doohan, who was also still recovering from serious injury.
Among those to congratulate Hayden was Rossi, who sportingly reached out to shake his former team-mate's hand as he rode slowly past. Hayden then removed his helmet, as he has done in his three previous race victories, and carried an American flag before stopping and lighting the traditional end-of-race fireworks.
By that time Rossi had returned to the Camel Yamaha pits, where he was greeted by a round of applause. There was nothing either Rossi or his team could really say; he had simply made a mistake and could only offer a quick hug for each team member.
Meanwhile, Bayliss had sensationally led the race from start-to-finish - responding to late pressure from Capirossi to take his first ever MotoGP victory by 1.3secs as Ducati celebrated its first ever MotoGP one-two.
It was an incredible ride for the 2006 World Superbike champion, who spent two seasons with Ducati in MotoGP before being sacked at the end of 2004. The Australian veteran had then moved to Camel Honda, where his season was prematurely ended by injury, before moving back to Ducati and WSBK for 2006 with immediate title success.
Bayliss had never ridden a 2006 Desmosedici, or Bridgestone tyres, before this weekend - when he stepped in to replace the injured Sete Gibernau - but the Australian immediately adapted to the new machinery, underlining just how talented he is. MotoGP probably never saw the best of Bayliss during his full time career and, having signed to spend another two seasons in WSBK, the 37-year-old may never line-up on the grand prix grid again, but he can be immensely satisfied at having joined an exclusive list of MotoGP and WSBK race winners.
Meanwhile, second for Capirossi gave the Italian third in the championship by a single point over Melandri, fifth on Sunday, whose team-mate Toni Elias completed the top six.