Having flown into Singapore on Sunday, Blair spent hours, day and night, charming International Olympic Committee members one-on-one before jetting out in the early hours of Wednesday to host this week's G8 summit in Gleneagles, Scotland.
His efforts proved decisive as London overhauled the long-term favourites 54-50 in the final round of voting to become the first city to be awarded the richest prize in sport for a third time.
Madrid, New York and Moscow had dropped out in the previous rounds.
"It is a momentous day for London," Blair said from Gleneagles on hearing the news. "It is not often in this job that you get to punch the air and do a little jig and embrace the person standing next to you."
"We are taking home the biggest prize in sport," bid leader Sebastian Coe, the twice Olympic champion, told reporters in Singapore.
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French President Jacques Chirac had arrived in Singapore on Tuesday to add muscle to Paris's bid but it proved to be too little too late.
The Paris team were left in tears as their bid failed at the last hurdle -- a third rejection in 20
"It's hard ... It's a great disappointment, a great emptiness around us all," French sports minister Jean-Francois Lamour told reporters in Singapore.
"We gave the best we could, we spoke from our guts, with our heart ... but it seems it didn't convince the IOC."
The London-Paris rivalry had appeared to intensify in recent days because of comments attributed to Chirac criticising British food.
French media had also widely reported suggestions that Britain was using underhand tactics in last-minute lobbying to win the Games, notably by openly sniping at the French plan.
Chirac thanked the French bid team for their "commitment, professionalism and the spirit of fair play that had always guided it".
BLAIR EFFECTIVE
Paris bid chief and former diplomat Philippe Baudillon was philosophical in defeat. "We are very, very disappointed but it was a very good competition. We thought we could win but obviously we did not. Ah well, that's life."
IOC members and the British bid team agreed Blair had made the difference.
Irish IOC member Patrick Hickey said: "This is down to Tony Blair. If he hadn't come here I'd say that six to eight votes would have been lost and London would not be sitting here today winners.
"The four votes that were in it in the final round were definitely down to him.
"Chirac came far too late."
London 2012's senior vice-president Andrew Craig paid tribute to the Prime Minister's efforts.
"Over time we found people we wanted to put in front of our politicians. Tony Blair saw about 25 members of the IOC, it was back-to-back, non-stop and the anecdotal feedback was that this was very effective."
IOC members also paid tribute to Coe who stepped in to become London's bid chief a little over a year ago after American Barbara Cassani stepped down.
"ABSOLUTELY ECSTATIC"
The former twice Olympic champion worked tirelessly and racked up tens of thousands of air miles to promote London's candidacy.
"Sebastian Coe was absolutely superb and his presentation to the IOC members on Wednesday was key, I am sure," German IOC member and vote scrutineer Thomas Bach said.
"I am convinced it made the difference because, you know, there were many members who arrived here in Singapore undecided. They thought they would wait for the presentation and London were very impressive."
As IOC president Jacques Rogge read out the answer to the question the world had been asking, London's bid team burst into a chorus of cheers and mobbed Coe.
Chirac was in the air on his way to join Blair at Gleneagles and his office offered congratulations to the London team.
"The head of state congratulates the city of London. He wishes good luck and full success to the British authorities and people in the organisation of the 30th Olympiad."
