(CBS News) London is about to be overrun by thousands of athletes and millions of spectators as the Olympics begin in 11 days.
The biggest question is, will there be enough security? London has been targeted by terrorists, including the subway and bus bombings in 2005.
The first wave of athletes streamed through London's Heathrow Airport. For most, it was a smooth run.
Later though, U.S. champion hurdler Kerron Clement got stuck on a bus that lost its way.
"Um, so we've been lost on the road for 4hrs," He tweeted. "Not a good first impression London."
A bigger scandal over Olympic security is leaving an even worse impression.
The British Army will be the foundation of the games' security, but to back the soldiers up, there was supposed to be another army of civilian security guards provided by a contractor: G4S.
The company promised to provide 16,500 of civilians to guard the games, but suddenly, with only two weeks to go, G4S announced it couldn't deliver.
So Teresa May, Britain's Home Secretary, announced "plan B."
"We have the finest military personnel in the world. Troops who are willing ready and able to step in when their country calls," May said.
In other words, they will send in another 3,500 soldiers. Then on Monday it emerged that some venues would still be short of guards, so there was a hasty "plan C": Re-assign local police.
No one thinks the last minute changes will seriously compromise Olympic security just the credibility of the London organizers.