Britain deployed 1,200 more soldiers to secure the Olympics on Tuesday, as embarrassed organisers scrambled to fill a shortfall left by a private firm hired to guard the Games just three days before the opening ceremony.
Police stressed, however, that they were content with security arrangements for the greatest show on earth, which kicks off in Cardiff in Wales on Wednesday with a soccer match between the women's teams of Britain and New Zealand.
Hundreds of thousands of visitors have descended on London from around the world and a million extra people are expected in the city every day of the July 27-Aug. 12 event, putting pressure on a creaking transport system some of which dates from the 19th century.
Yet for all the grumbling by a notoriously critical media and Londoners braced for disruptions to their daily lives, the sense of excitement is palpable with the Games just around the corner and the sun shining brightly after weeks of rain.
And the early buzz from Monday evening's technical rehearsal for the opening ceremony at the main stadium of the sprawling Olympic Park was positive, suggesting film-maker Danny Boyle's unusual, quirky and ambitious vision might just work.
"I'm very satisfied that we're in a very good place," said Chris Allison, Britain's national Olympic security adviser, when asked whether he was happy with arrangements in place to deal with any possible terrorist threat.
"We've done all the planning, we've looked at the way in which terrorists have attacked in the past and we try to make sure that none of those could get through our security measures," he told reporters at a daily Olympic briefing.
About 11 million visitors will witness the thrill of victory and despair of defeat as some of the world's greatest athletes, from Jamaican sprinter Usain Bolt to U.S. swimmer Michael Phelps, battle for the ultimate prize in sport - Olympic gold.
The Games will cost nine billion pounds ($14 billion) to stage, and in spite of criticism of the outlay during straitened economic times, officials have defended the spending as most goes into regenerating run-down east London for the long term.
As well as a flood of ordinary people, luxury yachts of the super-rich have moored close to the stadium and amongst expected dignitaries are Russian President Vladimir Putin, presidential candidate Mitt Romney and U.S. First Lady Michelle Obama.
Security is a sensitive issue in London, hit by suicide bomb attacks in July, 2005 that killed 52 people. They struck the day after the capital was awarded the 2012 Games.
And the issue has taken on added significance in the 40th anniversary year of the 1972 Munich attack by Palestinian militants that killed 11 Israeli Olympic team members.
Their widows arrive in London on Wednesday to pressure Olympics organisers to mark the tragedy, stepping up a long campaign to organise an official commemoration.
Romney joined the debate, saying he supported a minute's silence at Friday's opening ceremony, and Olympic chief Jacques Rogge paid a surprise tribute to the athletes in London on Monday.
Around 30,000 people, including family members of the huge cast of men, women and children taking part, filled the main Olympic stadium on a balmy Monday evening for the first open rehearsal of the opening ceremony.
Boyle's pleas for details of the event to remain secret and off the public pages of Twitter and Facebook.
The opening ceremony mastermind has voiced frustration at the media and members of the public who have leaked elements of the ceremony, which is inspired by William Shakespeare's play "The Tempest" and has a strong musical element.
What is officially known is that the first sequence recreates a pastoral idyll, complete with geese, sheep, horse and cart, fields, fences and a game of village cricket. The ceremony is expected to be artistic and intimate compared to the Beijing opening extravaganza.
What the media has since leaked includes elements of the next "act" of the show, recreating the "dark Satanic mills" of William Blake whose poem including this reference to the Industrial Revolution became an anthem to England.
Even at the full rehearsal there were key moments missing, and mystery surrounds both the location of the Olympic cauldron and the identity of the individual given the honour of lighting it in front of a television audience of more than a billion.
"We can't show you everything," Boyle said in a brief introduction to the action-packed, stunt-filled show. "If you would not tweet and you would not post, especially pictures, we would really, really appreciate it."
HERE COMES THE SUN
At Tuesday's Olympic briefing, questions focused on security and transport, areas where the government and Olympic organisers have come under fire from opposition politicians and the media and where concerns remain.
The extra troop deployment, taking the military contribution to the Games to well over 17,000, was to cover the shortfall left by private security group G4S.
The company caused a scandal by announcing it would fail to meet its target for the number of guards it could provide, and on Tuesday said that it had around 5,800 security personnel deployed, still short of its revised objective of 7,000.
On transport, passport officials and some train drivers plan strikes at key periods of the Games, and London's metro and overland rail networks showed the strain this week with three lines serving the Olympic Park severely disrupted on Monday.
London's "Games lanes", reserved for Olympic officials, athletes, sponsors and the media, open on Wednesday, raising the prospect of further complaints from the city's famous black taxis and regular motorists who are excluded from the system. Londoners have labelled them Zil lanes after Soviet limousines given special privileges.
But for all the complaining, the London 2012 chief executive had other issues on his mind.
"My biggest worry is actually the weather," said Paul Deighton, adding that much of the construction was carried out in torrential rain in recent months.
"We've got a lot of events that are outside. I think the impact the weather has on people's mood, how they enjoy the games, is very big.
"So for me, if I have a prayer I could make, it's every extra day of sunshine just makes for a better experience for everybody here in town."
And the forecast? Hot sunshine until Friday, when light showers are predicted.