Colin crowned 'King' of Hollywood on a night of high emotion in the Kodak Theatre
The 50-year-old was quite clearly humbled as he walked up on stage to receive his best actor Academy Award, which he dedicated to his mother, Shirley.
He thanked "all the people who have been rooting for me back home" and his wife Livia for "putting up with my fleeting delusions of royalty" in his self-deprecating acceptance speech.
"I have to warn you that I am experiencing stirrings somewhere in the upper abdominals that are threatening to form themselves into dance moves," he added. "Joyous as they might be for me, it would be extremely problematic if they made it to my legs before I get offstage."
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Colin's win marked a very successful night for The King's Speech, which picked up four Oscars in total.
It was named best film – beating competition from Inception, True Grit, Black Swan and The Fighter – and the man behind the historical movie, Tom Hooper, received the best director trophy.
"Thank you to my wonderful actors, the triangle of man-love which is Colin Firth, Geoffrey Rush and me," he said as he dedicated the award to his mother, whom, he revealed, had first suggested he make the movie after watching a script read of the stage version.
Perhaps the most poignant win of the night belonged to 73-year-old London-born writer David Seidler, who wrote the screenplay for The King's Speech.
David – who himself overcame a debilitating stutter as a child - told the audience in the Kodak Theatre that as a young boy he had listened to the King as he rallied the empire against Nazi Germany.
And then in 1982, he revealed, he wrote to the Queen Mother asking permission to tell her husband's story, but that she had asked him to wait until after her death.
"I accept this on behalf of all the stutterers in the world," he said. "We have a voice. We have been heard."
Natalie Portman beat competition from Annette Bening, Nicole Kidman, Jennifer Lawrence and Michelle Williams to be named best actress.
Always the clear favourite to win for her performance as a disturbed ballet dancer in Black Swan, the pregnant actress thanked her parents and her "beautiful love Benjamin Millepied who choreographed the film and has now given me the most important role of my life".
The emotional 29-year-old star – who, like Colin, had already seen success at the Baftas and Golden Globes – also paid tribute to her co-nominees, saying, "I truly wish that the prize tonight was to get to work with my fellow nominees – I'm so in awe of you."
Stars of The Fighter fought off other best supporting contenders for Oscars glory.
Wales-born Christian Bale took home his first Academy Award for his portrayal of drug-addicted former professional boxer Dicky Eklund.
"What a room full of talented inspirational people – what the hell am I doing here?" he said before paying tribute to his wife Sibi - "my mast through the storms of life".
Best-supporting actress Melissa Leo, who stars as Christian's mother in the film, had broadcasters in a panic after she accidently used an expletive at the podium.
They had to bleep out the offending word and she later apologised saying it had been "inappropriate".
"Really, really, really truly wow," said the visibly shocked actress, who received her Oscar from Hollywood legend Kirk Douglas.
"I know there have been a lot of people saying some real, real nice things to me for several months now, but I am just shaking in my boots here."
It was a disappointing night for The Social Network which missed out in all major categories but won three Oscars for screenplay, original score and film editing.
Leonardo DiCaprio sci-fi vehicle Inception took home four Academy Awards for cinematography, sound mixing, sound editing and visual effects.
Other standout moments included performances from Celine Dion and Gwyneth Paltrow, while co-presenters Josh Brolin and new dad Javier Bardem – attending with wife Penelope – danced their way on to the stage together to hand out a trophy.
At one point James Franco appeared on stage with his co-host Anne Hathaway - the youngest ever Oscars hosts – dressed as Marilyn Monroe. "I just got a text from Charlie Sheen," he joked.
Oscars 2011: List of winners
- Best Film: The King's Speech
- Best Actor: Colin Firth
- Best Actress: Natalie Portman
- Best Supporting Actor: Christian Bale
- Best Supporting Actress: Melissa Leo
- Best Director: Tom Hooper
- Best Original Screenplay: David Seidler
- Best Adapted Screenplay: The Social Network - Aaron Sorkin
- Best Foreign Language Film: In A Better World - Denmark
- Best Animation: Toy Story 3
- Best Art Direction: Alice in Wonderland
- Best Cinematograpy: Inception
- Best Sound Mixing: Inception
- Best Sound Editing: Inception
- Best Original Song: We Belong Together, Toy Story 3
- Best Original Score: The Social Network, Trent Reznor and Atticus Ross
- Best costumes: Alice in Wonderland
- Best Documentary Feature: Inside Job
- Best Documentary Short: Strangers No More
- Best Film Editing: The Social Network
- Best Animated Short Film: The Lost Thing
- Best Live Action Short Film: God of Love
- Best Visual Effects: Inception
- Best Makeup: The Wolfman