By Jane Mower
BBC News, London
Seconds after London was proclaimed the Olympics winner the crowds that had packed into every inch of Trafalgar Square were sprayed with confetti.
Confetti filled the air as London was proclaimed winner
A shocked look on Dame Kelly Holmes' face was mirrored throughout the crowd as they absorbed the news that London had won.
It was very clear that although no-one had doubted London's ability to host the Games, many had not been totally convinced it could actually happen.
Jubilant scenes followed with flags waving, people clapping, cheering and hugging each other and many capturing the moment on mobile phones.
And for some beating the French made the victory all the more sweet, with one man voicing his disappointment that the cameras were not showing the reaction in Paris.
Then catching most people off guard, the Red Arrows flew overhead leaving their trademark blue, red and white smoke trails in an unannounced fly-past.
Some bemused-looking tourists were caught up in the excitement but for most people it was a welcome distraction during their lunch break from work.
People in the crowd used mobile phones to pass on the good news
Jane Clarke, 48, from Camden, north London, went to Trafalgar Square to enjoy the celebrations during her lunch break.
"It's fantastic, I am so over the moon. I was watching the announcement on a big screen at work and when I heard the result, my stomach just flipped."
Space was at a premium as more than 15,000 crammed into Trafalgar Square, spilling into the nearby roads.
Passengers on the top deck of passing buses watched the scenes from their vantage point as traffic came to a standstill and trucks honked their horns in approval.
As television cameras panned a deceptively sunny-looking Trafalgar Square the crowd enthusiastically waved their flags, eager to show their support for the London bid.
Gordon Mc Sweeney, 53, who lives 3 miles from the site of the Olympic Village in east London, was fully behind the bid all the way.
"London is without a doubt one of the most fantastic cities in the world. It has so much going for it and so many great ideas."
Earlier, listening intently to the voting procedure and willing London on to the final stages the spectators had cheered at the news the vote had come down to London and Paris.
The feeling that it could easily have gone either way was evident in what had become a nail-biting finale.
Bus passengers enjoyed their vantage point
Just minutes before the announcement, in true British style, a few spots of rain appeared and umbrellas popped up around the square.
An expectant crowd waited patiently as the envelope containing the winning city's name was opened and the president of the International Olympics Committee announced that London would host the 2012 Olympic Games.
As a cheer went up across the square a frenzy of text-messaging and phone calls began, everyone desperate to let the world know that Great Britain will host the 30th summer Olympic Games.
Kat Law, from Wimbledon, south-west London, was travelling on a bus into Trafalgar Square when the result came through.
"We just screamed with delight and the whole bus started cheering," she said.
Thrilled with the result Lilly Hockley, 74, of Tower Hamlets, south-east London, said: "We will be able to stand up with pride and it will be good to see something big going on in London."