A senior Olympic figure has told the BBC that London only won the 2012 Olympics because of a misplaced vote.
BBC News 24's report on the matter can be seen on Sunday, 25 December
Alex Gilady claims the mistake happened when a vote was cast for Paris instead of the intended recipient, Madrid.
Had the vote gone to Madrid, claims Gilady, they would have finished level with Paris on 32 votes apiece in the penultimate round, behind London.
Gilady suggests Madrid would have won a head-to-head vote with Paris and gone on to beat London in the final round.
Gilady, from Israel, is a senior member of the International Olympic Committee (IOC) and a member of the IOC's London 2012 Co-ordination Commission.
He told BBC News 24 that the incident occurred in the third round of voting in Singapore in July.
"London was ahead, but Paris and Madrid were 33-31 in the votes," said Gilady.
"Let's say what we think now happened, that one member made a mistake and voted for Paris rather than Madrid.
"If he had voted for Madrid it would be 32-32. We would have to have had a vote-off.
"In the vote-off all the votes supporting London would go to Madrid, because the fear was that Paris had a big chance to win.
"Madrid would then have won against Paris.
"Coming to the final against London, all the votes from Paris would have gone to support Madrid.
"Madrid would have won.
"That is now what we think happened. This is what you call good fortune and good luck."
A News 24 investigation appears to support Gilady's suggestion.
However, Craig Reedie, a British member of the IOC and former British Olympic Association chairman, dismissed the claims.
"The story is totally irrelevant, the voting was conducted in a secret ballot under the rules of the IOC, absolutely properly, all votes were properly recorded," he told BBC Radio Four's Today programme.
"If Alex is claiming that an unnamed member 'might' have done something which 'might' have brought about something else which 'might' have brought about a different voting structure then I'm afraid that this is the kind of tittle-tattle that happens after many an IOC vote.
"London won the Games hands down. If you're looking for reasons for London's win I suspect you should probably look at the quality of the bidding effort that went in Singapore and the quality of the lobbying effort, and above all the quality of the presentation."
During the 2012 vote there was a long delay before the result of the third round was announced, which occurred because a Greek IOC member complained about his vote.
At the time it was assumed someone had failed to vote in time, but it is now clear that all members had voted.
In final round of voting, London beat Paris 54-50 to win the right to host the 2012 Olympics.
A London 2012 spokeswoman said: "There are a lot of folklore stories about who voted for whom.
"At the end of the day, it was a secret ballot. This is the opinion of one individual. The result is what matters and we are not going to be drawn into speculation."
Feliciano Maroyal, the chief executive officer for the Madrid 2012 bid, told the Times: "We were very close to winning.
"We can never know if the Greek vote would have been decisive, but it is lamentable for one human error to have ruined all our hard work which we put in trying to win the Games."