Serena Williams clenches her fists and lets out a great shriek.
"Errrrgh!" And another. "Errrrgh!"
She cannot wait for London 2012 but the subject of the Olympics brings back the memory of her quarter-final defeat in the singles in Beijing. Hence the explosion of frustration.
"2010's just around the corner," says Serena. "Venus and I are so going to be there. We are already talking about how exciting that will be on grass. What a great moment.
"But I could have won the singles last time. I was up 4-1 against the girl who went on to win it [Elena Dementieva] with an easy shot to go 5-1. And I lost."
Clearly, it still rankles, even though she has won gold twice in the doubles with sister Venus in 2000 and 2008.
At 28, however, the ambition still sparkles from Serena like the huge silver earrings and bangles she is wearing as she relaxes in London's Dorchester hotel.
She is here to plug her autobiography, 'Queen of the Court', published by Simon & Schuster, with a whistle-stop round of interviews - after winning the end of season tournament in Doha when she beat Venus in the final and regained her ranking as number one in the world.
She also picked up a cheque for 950,000 pound, which already she has made a small dent in by buying eight rugs for her new house and a dress for herself.
The Williams story is the most extraordinary in sport. A tale of sibling love and rivalry. And a dad and mentor in Richard who read that top tennis players could earn a fortune and told his wife Oracene that they would have two daughters who would dominate the sport.
The rest is history. How the sisters had to duck to avoid the bullets of drug gangs on the courts in Compton, California.
How they were taught at home and only allowed to practise against adults.
How the dad's dream came true when at 17 Venus reached the final of the US Open at her first attempt and two years later, Serena, also 17, won it.
A decade later Serena has 11 Grand slam singles titles to her name, Venus seven.
"The best champions don't play for money," says Serena. "Everybody these days wants to be famous, wants to get rich quick. But it's about putting a lot of hard work into it. People lose sight of that. People who are the best of the best they work hard. It didn't come overnight.
"I was doing this since I was three. I didn't make it until 15 years later. That's a lot of time and effort."
The rewards have been colossal. Serena's prize winnings alone stands at almost 17million pound, more than any other woman in tennis.
Her sponsorship deal with Nike is worth £24.5million. Then there's an acting career which has seen her appear in ER and Law & Order, and a fashion range called Aneres - her name backwards.
And the book, which among other things sees her face up to her emotions in the wake of the killing of her big sister Yetunde in a drive-by shooting on September 14, 2003.
She says: "After that tennis was about the last thing on my mind. It didn't seem important. I went through the motions of rehabbing and keeping in shape, but my heart wasn't in it and my head wasn't