To test the point, try navigating parts of West London when 82,000 rugby union fans are spilling out of Twickenham Stadium; or try crossing the city by road when highways are closed for the annual London Marathon.

Now multiply those tribulations by many degrees and imagine a capital city in July and August committed to the Olympics to the exclusion of its normal crop of tourists, theatergoers or conventioneers.

The West End theater district, said the composer and impresario Andrew Lloyd Webber, is facing “a bloodbath of a summer” because theatergoers can neither find nor afford hotel rooms in a city filled with sports fans. “People who want to go to the theater or concerts are not the same sort of people who really want to go to sport,” he said.

But duality has accompanied the London Games from their beginnings.

For every announcement of stadiums built or rail links upgraded, there have been reports of cost overruns.

London secured the right to host the Games at a time of economic boom when the nation seemed afloat on surging credit. Now, the city is obliged to stage them after the bust of the global economic crisis when jobs are lost and times are hard.

“You can say: These are times of austerity, and therefore we should pare them down as much as possible,” said Jeremy Hunt, the British culture secretary. “Or, you can say: Because these are times of austerity, we need to do everything we possibly can to harness the opportunity of the Olympics.”

Britain has chosen the latter course. That is not really surprising: official enthusiasm has rarely seemed to wane or falter.