The women's 800 freestyle

Coming into today's 800 freestyle, Londoner Rebecca Adlington was the 1 - 2 betting favorite with the British bookies, meaning you had to bet two dollars on her to win one. She was the defending Olympic champion in the 800 free, the world record holder at 8:14.1 (a time set in a tech suit), and had the fastest time in the world so far this year at 8:18. Fifteen year old Katie Ledecky, who had won the US Olympic Trials with an 8:19, was going off at 18 - 1, meaning if you bet one dollar on her to win, you could get eighteen in return.

Adlington was the one with the royal swimming pedigree. But she had swum her 400 earlier this week in 4:03.0, eight-tenths of a second slower than she had gone at British Trials in March, so it seemed unlikely that she would improve much on her 8:18 from March.

Ledecky, on the other hand, had been doing best times virtually every time she swam since January. At the beginning of this year, she had never broken 4:10 for a 400; by Trials she went a 4:05.0. Likewise, she'd never broken 8:33 for the 800 until early this year. If you extrapolated from her recent performance curve, it seemed a pretty safe bet that her next swim would be an improvement as well.

So Adlington had the credentials, but Ledecky had the momentum.

The TV announcers kept saying that the British swimmers were being helped by the roar of the hometown crowd. But to this point, the only British swimmer who had performed up to expectations was 200 breaststroker Michael Jamiesen (who in fact performed beyond them). Virtually every other British swimmer had fallen short. The pressure from that hometown crowd evidently cut both ways.

Adlington must have felt the weight of the world on her shoulders.

Fifteen year old Katie Ledecky felt no such pressure. She had the fearlessness of one blithely unaware of all the history that the Olympics represented. Plus her quote from earlier in the week was heartening: "I'm just having so much fun being here with everybody." If Ledecky had been paralyzed with nerves, she would likely not have said that. Mindlessly upbeat is usually the appropriate frame of mind for fast swimming, and that outlook comes naturally to 15-year-olds.

Given all this, why were the pre-race odds so skewed toward Adlington? People -- bookmakers included -- tend to be overly impressed by resumes, and in swimming, there is no resume more impressive than "Olympic champion and world record holder."

On top of that, the odds were being set by British bookmakers, in Britain, on a British woman who is very popular at home. All the sentimental money which poured in for Adlington from her countrymen undoubtedly helped skew those odds.

A lot of people seem to bet with their hearts rather than their minds. This certainly doesn't make them bad people. It does, however, make them people you want to bet with.

Ledecky won with an 8:14.6, the fastest time in textile ever, a Spanish woman got second in 8:18.7, and Adlington got third in 8:20.3.