David Hoskinson, a photographer who has been covering Olympic events for 20 years, has firm opinions on why women's beach volleyball is so popular with corporate sponsors. "You know this, you're a bright girl," he sniffs at me. "It's a three-letter word. It's not complicated. Sex sells."
Horse Guards Parade is crowded with families in expensive leisurewear and corporate guests in branded lanyards waiting for the beach volleyball. It's not a traditional British sport. However, of the Olympic events for which government officials and sponsors have been permitted to block-book tickets, women's beach volleyball is among the most popular – the Government bought 410 tickets at a cost of £26,000, compared with only 256 athletics tickets. The sport, largely known for the tiny costumes of its female competitors, is also a hit with sponsors such as Visa and Coca-Cola.
One of those I meet outside, Andrew Monk, 42, works for Coca-Cola. "I'm bringing a customer as part of our contact strategy, because we both wanted to come," he says. "That's how our businesses talk to each other – Coke as a corporate sponsor has had [these tickets] for years."
Since it became an official Olympic sport in 1996, beach volleyball has, perhaps unfairly, been known more for the skimpiness of its costumes than the intricacies of its gameplay.
Yes, costume size is expressly specified in the rules – this year, for the first time, athletes are permitted to wear shorts rather than bikini panties, to a maximum length of 3cm above the knee – but professional beach volleyball is a serious and gruelling game, and playing it at an international level involves years of dedicated training. From the way beach volleyball is discussed you'd think that players were selected by submitting their bust-to-waist ratio and a statement of their willingness to bend over and show their buttocks to world leaders. This sort of assumption does a great disservice to the players.
Except, perhaps, to Misty May-Treanor, the American team member who in 2008 invited spectator and then-President George W Bush to smack her on the bottom with the words "Mr President, want to?"
A few spectators are extremely clear on why they came to this event. "What do you mean why?" says Chris Higgins. "Because of the women!" He and his friend Andy Naisbitt are both wearing T-shirts bearing the legend "Women's Beach Volleyball Coach", although in fact Andy admits that he didn't know the rules at the start of the game.
"It was one of the best mornings of my life," says Andy. The best bit? "Probably the girls dancing." The actual competitors are not in fact required to wiggle around with beach balls in their bikinis, so separate teams of dancers and singers have been employed for half-time, an unusual practice for Olympic matches, but then, as another spectator, Damien Walter, comments: "I'm not sure how much of a professional volleyball-supporting crowd it was there."