Gabby Douglas declared American gymnastics domination as she wrapped up the women's individual all-around title to sit alongside her team Olympic gold.
Douglas, the 16-year-old, whose nickname "the Flying Squirrel" has been borne out by the heights she is hitting at London 2012, outscored Russia's Viktoria Komova by 0.259 marks.
Great Britain's Rebecca Tunney, 15, finished 13th on her Olympic debut.
"It's been an amazing experience; the best week of my life," she said.
"To compete at a home Games in front of this crowd has been incredible.
"To be the youngest in Team GB I'm very proud and I've learnt so much. I'm looking forward to the rest of the Games, the atmosphere and cheering on Team GB."
British team-mate Hannah Whelan finished in last place after scoring zero marks for her vault.
Whelan, who had her eyes on outstripping Becky Downie's 12th place for Britain at the Beijing Olympics, completely lost her vault landing and was sent sprawling. The judges gave her no score.
Medals, though, were always out of British reach as American and Russian superstars fought for the honours inside the North Greenwich Arena.
Douglas and team-mate Aly Raisman had devastatingly deposed US colleague and 2011 world champion Jordyn Wieber - a pre-Olympic favourite - going through to the final at the expense of Wieber as rules allow only two qualifiers per nation.
And while Raisman faltered on the uneven bars, Douglas maintained that momentum throughout the final, hitting her routine on each of the four pieces.
The Americans are renowned for their vaulting and Douglas's, at 15.966 the highest of the competition, put pressure on Russia's Komova and Aliya Mustafina from the outset.
Mustafina, the 2010 world champion, took herself out of the reckoning when she fell from the beam, leaving Douglas and Komova to decide the Olympic title with their floor routines.
Though Komova, 17, narrowly outscored Douglas, it was not enough to stop the American becoming her country's third consecutive women's all-around champion.
Mustafina won a tie-break decision for bronze after she equalled Raisman's score of 59.566. The Russian "had a higher sum of final apparatus scores, adding the total of her top three apparatus scores," said a statement from the sport's organisers.
Douglas won with 62.232 ahead of Komova's 61.973. Tunney earned 56.932 whereas Whelan's score, affected by her zero on vault, was 41.999.
Whelan says she will take some time off after the Games, on the back of a deeply disappointing outing, but Tunney will take great encouragement from her 56.932 score, fractionally outside the top 10. She will still be a teenager by the time Rio 2016 comes around.
Beth Tweddle is the lone female Briton left to compete in a gymnastics final at London 2012, with a place booked in the uneven bars final on Monday, the day after Louis Smith goes in the pommel horse final.
Kristian Thomas competes immediately after Tweddle in Monday's men's vault final.