The first competitors are due to take up residence in the Athletes' Village for the London Olympics, after a weekend in which the security of the event was called into question.
The first of the Olympics Games Lanes also comes into operation on the recently repaired and reopened M4, hours after the Government refused to rule out the prospect of drafting in more troops in the wake of the G4S security fiasco.
With less than two weeks until the opening ceremony, ministers insisted the Games would be secure and dismissed the firm's failure to provide the promised 10,000 security guards as no more than a "hitch".
On Sunday, however, it emerged that they had been warned 10 months ago in a confidential report by HM Inspectorate of Constabulary (HMIC) about concerns over security.
Culture Secretary Jeremy Hunt was at pains to defend G4S from criticism, even going so far as to suggest it was "completely normal" for firms to break their contractual commitments on large projects.
"G4S have been quite honourable. They have put their hands up. Nick Buckles, the chief executive, has said they got it wrong, they have apologised, they are going to cover all the costs, he has apologised to the troops who are going to be drafted in at the last moment," he said. "I think it is completely normal that you are going to find some contractors on a project of this size who aren't able to deliver what they have promised."
But pressed on whether the 3,500 additional troops who have been brought in to make up the shortfall would be sufficient, he said: "We have contingency plans for all eventualities."
Mr Buckles, who is due before the Commons Home Affairs Committee on Tuesday, has admitted he may be forced to quit his £830,000-a-year job in the wake of the Olympic debacle. He told the Sunday Telegraph the episode was a "big setback" but he plans to stay to help the company deliver the contract, after which his future will be decided by shareholders.
London 2012 chairman Lord Coe denied security had been compromised and appeared to lay blame for the problems with the staff hired by G4S.
He said: "It was only when the rubber hit the road that we were able to see, as G4S identified, a gap. The reality is, and I cannot put this any more simply, when they expected people to materialise, they simply didn't. That is why we moved quickly to stem that gap."
The Home Office, meanwhile, confirmed that ministers had received a report from HMIC last September raising a number of "issues to be addressed" with the Games organising committee, Locog, although it said these had already been dealt with.
In a display on Sunday US choreographer's Elizabeth Streb's troop of acrobatic dancers could be seen "bungee dancing" off the Millennium Bridge and abseiling down City Hall in honour of the Olympics.
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