The match in the Welsh capital Cardiff comes two days before Friday's opening ceremony at the main London stadium but marks the competitive sporting debut for the Games, the culmination of seven years of preparation for the greatest show on earth.
In host city London, basking in sunshine after a rainy summer, authorities went ahead with unpopular lane closures to keep the roads – and hundreds of thousands of extra visitors – moving and security has been beefed up to protect the Games.
More than 16 000 athletes are warming up for their big day at venues across Britain, and some 11-million visitors, and a global television audience of billions, will follow the July 27 to August 12 Olympics.
Usain Bolt, Jamaican winner of the 100m and 200m Olympic titles in Beijing in 2008, fired the opening salvo in what promises to be a classic 100m sprint final on August 5, the highlight of the Games.
"This is my time," said the 1.95m athlete, as attention turns from a security scandal and transport chaos in the run-in to the Olympics to what really counts – sport.
"This will be the moment and this will be the year, when I set myself apart from other athletes in the world," 25-year-old Bolt told the Guardian newspaper.
Bolt, who holds the world record for the 100m race, is aiming to achieve what no other man has ever done before – successfully defend the 100m and 200m finals.
While the British government and Olympic officials will be delighted that sport is now in focus, the threat of transport disruption and security worries lingered with just two days to go before the eagerly-awaited opening ceremony.
One target of anger among notoriously grumpy taxi drivers and many ordinary Londoners are the so-called "Games lanes" which came into operation on Wednesday.
Dubbed "Zil" lanes after Soviet roads reserved for black limousines carrying senior Communist party members, the roads are reserved exclusively for Olympic officials, the media, athletes and sponsors.
Anyone caught straying into the lanes without permission faces an automatic £130 fine and there has been confusion and heavy traffic in several parts of the capital as a direct result of the system.
'Pain in the neck'
"They've closed off the Games lane but nobody [from the Olympic community] was using it," said Ross Keeling, a call-out engineer, speaking after he travelled from east London to the city centre.
"My journey usually takes me 40 minutes but it took two hours with the change. It was a pain the neck. We just have to sit and watch the empty lane."
The threat of delays at Heathrow and other airports was avoided when border guards called off a strike planned for Thursday.
Culture and sport secretary Jeremy Hunt said that fears over long queues at immigration control during the days leading up to the Games had been avoided.
"One of the big successes of the last few weeks has been that queues at Heathrow have been the dog that didn't bark," he told BBC radio.
Hunt said on Tuesday that 1 200 extra soldiers had been deployed to protect Olympic venues at the last minute to cover for a shortfall in private security guards in a major embarrassment for Prime Minister David Cameron's administration.
Counter-terrorism chiefs have played down the possibility of a major attack on the Games.
The symbolic Olympic torch, nearing the end of its 8 000-mile journey, on Wednesday visits Wembley Stadium, scene of England's only soccer World Cup triumph in 1966 and will be carried by the goalkeeper in that match, Gordon Banks.
Its odyssey ends with the lighting of the Olympic cauldron on Friday evening in the presence of 60 000 spectators including Queen Elizabeth, US First Lady Michelle Obama and a host of celebrities and dignitaries.
Another one billion people are expected to tune in around the world for the ceremony directed by filmmaker Danny Boyle.
While many details of the show have leaked through the media and social networking sites, some secrets remain, notably the identity of the person who will light the flame and even the location of the cauldron.
Former England and Manchester United soccer player David Beckham has confirmed he will play a cameo role in the quirky event, which will feature pyrotechnics, a celebration of British music and culture and several spectacular stunts. – Reuters