With the world's biggest sporting event taking center stage on their home turf, it's a safe bet that London betting houses are taking some big risks in hopes of turning some big profits.
The thing about bets is you can never really be sure how they'll turn out, just ask Rupert Adams, of British betting house William Hill.
“I think we were betting that USA would be first, then China, then UK,” Adams told NBC 6. “Looks like we were right with UK, looks like China and the USA will be the other way around.”
Welcome to the topsy turvy world of sports betting.
It's legal in the UK, where bookies pour over data, crunching every number, to stack the odds ever-higher against you, the bettor.
Then, sometimes, in the blink of an eye, the odds can favor you - especially, in the Olympics, where bookies aren't always experts in sports like badminton.
“If you do get involved in it, and do take it very sensibly, it's a great chance you'll actually beat the bookies,” Adams said.
Jamaican sprinter Usain Bolt did.
British gambling firm Ladbrokes cut Bolt's odds of winning Sunday's 100-meter to just one out of four, after his sluggish semifinal.
But, on race day, Bolt struck - making history by earning his second gold in the 100 meter since Beijing.
The win forced Ladbrokes to pay out $800,000 to bet winners.
Ladbrokes now calls Bolt, the most expensive Olympian of all time.
That's why William Hill is Bolt-proofing its bets.
Only a false start triggers a pay out, and those odds aren't high.
“Usain Bolt is nine to one to false start in the 200 meters, so if you place one pound, you win nine, walk away with 10,” Adams said.
If you're betting on an easy payday by putting it all on LeBron James and USA basketball's latest dream team, bet somewhere else.
“We don't want anyone to put money on the dream team, because we are that confident they're going to go on and win,” Adams said.