London's winning bid for the 2012 Olympics could have been helped by an International Olympic Committee (IOC) member pressing the wrong button during the voting process, according to a BBC report.
The report says that the member mistakenly voted for Paris in the third round of voting in Singapore on July 6, giving it 33 votes to 31 for Madrid instead of 32-32 which would have prompted a vote-off before the final round. Madrid had been ahead after the second round.
London then beat Paris 54-50 in the final round of voting, although it is widely believed that Madrid would have been a bigger threat to London had they got through to the final round.
The circumstances of the vote are to be screened by BBC News 24 on Sunday.
Alex Gilady, an Israeli IOC member and part of the London 2012 Co-ordination Commission, tells the programme that another IOC member, thought to be Lambis Nikolaou of Greece, made the mistake.
If true it would help to explain why Madrid had 32 votes in the second round of voting but lost one of them in the third round. The programme also suggests the mistake resulted in the long delay before the third round results were announced.
"Let us say we think we know what happened, that one member made a mistake and voted for Paris rather than Madrid," Gilady told the BBC.
"If he had voted for Madrid it would have been 32-32 and we would have to have a vote-off between Madrid and Paris.
"In the vote-off, all the votes supporting London would have gone to Madrid because the fear was that Paris had a big chance to win. Madrid would have won against Paris, coming to the final against London.
Reacting to the story a spokesman for London 2012 told the BBC: "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."
An IOC spokesman told Reuters on Friday: "We do not comment on voting intentions of IOC membership."
In an interview with Israel Army radio, Gilady said the IOC had known about the mistaken vote for nearly six months, although he told Reuters that the error had not necessarily been decisive.
"You need luck. But in order to get the luck, you need to do the hard work first," he said on Friday. "It was not as if the Games fell into London's lap off the back of a lorry."
A Greek source close to the Olympic movement told Reuters: How can Mr Alex Gilady know what any member of the IOC wanted to vote. The missing vote for Madrid in the third round could even be a case of one IOC member not voting.
"How can someone say there was a wrong vote. If something like that had happened wouldn't the IOC cancel the result and hold another vote?"