LONDON » What are the odds of a UFO sighting during the London Olympics opening ceremony? Or of the final torch bearer tripping as they ascend to light the flame? Or would you prefer a more traditional wager on the battle for gold between Russia and Spain in synchronized swimming duos?

London betting houses will offer odds on almost anything, including all 26 sports at the games, from the 100-meter dash to fencing, from diving to soccer. The industry expects to handle a record 100 million pounds ($155 million) in wagers during the July 27-Aug.12 competition — even some pretty outlandish parlays.

"We try to cater to most people’s tastes," said Joe Crilly, a spokesman for William Hill, a gambling house that encourages punters — the U.K. term for gamblers — to contact them with any bet they can dream up. They also offer online gambling in 182 countries, though not in the United States or in other countries where it is prohibited.

Ladbrokes, another British bookmaker, will offer 11,000 different wagers during the games, according to spokeswoman Jessica Bridge. Those bets include that the Olympics will be over budget, that a British athlete will be photographed eating a McDonald’s Big Mac, or that the athletes village in Olympic Park will run out of condoms.

William Hill offers perhaps the longest odds of the games: 1,000-to-1 that a flying saucer will appear over Olympic Stadium during Friday’s opening ceremony. Tough luck, presumably, if aliens don’t make first contact until the next day.

Other longshots get slightly better odds, like 250-to-1 that every team in the 4×400-meter relay final drops the baton, or 33-to-1 that flamboyant London Mayor Boris Johnson accidentally lights his hair on fire with the Olympic torch.

And this being famously soggy London, of course they are taking bets on the weather, paying even-money that rain will mar the opening night. If that’s not enough to make an Olympic fan cry, Ladbrokes will pay $50 on a $1 bet that it will rain every day, and 10-to-1 that a strike by transit workers will halt train service on the London Underground.

But the gambling story is not all fun and games.

The British betting industry is worth $9 billion a year, one of the biggest in the world, according to a 2010 study by accounting and consultancy firm Deloitte. Most houses offer online gambling as well.

There have been fears that the massive gambling volume could lead to corruption, which would forever mar London’s legacy. The IOC has barred athletes from betting on the games — and sports, police and gambling industry officials plan to meet daily to ensure that no illegal bets are placed.

Jacques Rogge, the president of the International Olympic Committee, has said previously that illegal betting can fuel the scourge of match-fixing.

Crilly said the betting industry is heavily regulated and immediately reports suspicious activity to Britain’s Gambling Commission.

"We have a lot of strict regulations in place to guard against any funny business," Crilly said. "If we were to see an unusually large bet for a sport we were not particularly expecting large amounts of money for, it would flash up … If there was any suggestion that it was suspicious we would get authorities involved."

The most heavily wagered event during the London games is expected to be the 100-meter dash, where Jamaican Usain Bolt, the reigning Olympic champion, is still the odds-on favorite despite a rough run-up to the games that saw him bested in trials by countryman Yohan Blake. Soccer will also be an extremely popular wager, as will the women’s heptathlon, where star British athlete Jessica Ennis is expected to compete for gold.

A major challenge for the gambling houses is setting the odds for the more obscure sports. Who is to say Dutch rider Adelinde Cornelissen should be a 15-to-8 shot in dressage, an equestrian discipline? Or if Sweden’s Anders Gustafsson should be set as a 9-to-1 shot in the 1,000-meter men’s single kayak race?

Crilly says ahead of the Olympics, betting firms assign teams to research each sport, spending weeks immersing themselves in facts and figures.

Punters can also bet on which country will win the overall medals table (the U.S. is favored, with China a close second), or how many golds the host nation will take home.

Bridge says Ladbrokes has already taken a 10,000 pound ($15,500) bet on Bolt to win the 100-meter dash and expects much larger wagers ahead of the big race.

"We anticipate our high roller customers will fancy him to do the business,’ she said. "If they were to want 50,000 pounds ($77,500) or more on Bolt, then we will happily lay it."