Wimbledon - Women: Williams and Kvitova survive Wimbledon openers
Four-times champion Serena Williams made an excellent start to Wimbledon, coming through an athletic first-round match against Czech Barbora Zahlavova Strycova that was tougher than the 6-2 6-4 scoreline would suggest.
The Czech, ranked 62nd in the world, was a dogged, determined opponent for the sixth seed on Court Two, chasing down every ball.
However, she found Serena's powerful first serve tough to handle, staggering backwards like a punch-drunk boxer when the ball thundered towards her.
Serena served for the match at 5-3 but Strycova broke her in a long ninth game, after forcing the American to slide across the grass to save two of three breakpoints.
Serena, who last won here two years ago, broke straight back, taking the victory on her second matchpoint and letting out a scream of joy when the Czech put a forehand long.
Serena, whose older sister Venus lost in the first round on Monday, will face Hungarian qualifier Melinda Czink in the second round.
She may hope to be on a bigger court next time, having wondered aloud at previous Wimbledon tournaments why she was so often scheduled to be on the smaller Court Two.
Asked about that complaint on Tuesday, Serena was reluctant to reply.
"I just can't talk about that right now, I'm not in the mood," she said.
She was more forthcoming when asked what she had learnt from her shock first-round defeat at the French Open last month.
"I learnt that... you've got to keep going," she said. "I was playing excellent before Paris.
"I was really disappointed, obviously I was extremely disappointed. But," she added with a laugh, "as Kelly Clarkson says, what doesn't kill you makes you stronger."
Serena said she was delighted to be have been confirmed on the US Olympic team on Tuesday and was looking forward to defending her doubles title with Venus next month at Wimbledon.
"I love playing doubles with her normally but especially at the Olympics. It's a whole another level. I really enjoy the opportunity to play with her, so it is real cool."
Petra Kvitova overcame a nervy start to the defence of her Wimbledon title to book her place in the second round with a 6-4 6-4 win over Akgul Amanmuradova.
Whether it was the swathes of empty seats to greet her arrival or her sluggish movement and frequently misdirected groundstrokes, there was little in Kvitova's first round victory to suggest she was the defending champion.
In contrast to number one seed Maria Sharapova, who treated a packed Centre Court to a regal display on Monday, the Czech showed little superstar quality as she nervously moved into the second round with a win over the Uzbek world number 96.
It is 12 months since the number four seed upset Sharapova to claim the title, but she looked ill-at-ease in the role of champion as she strolled out on Tuesday to begin her title defence.
It ended happily with the Czech saluting Centre Court with a smile and a wave, but it began in a flurry of unforced errors.
"I was nervous," she said during a rather swift press conference that extended to just three questions.
"It was first time for me to be as the defending champion of the grand slam. It was huge honour to come to the Centre Court.
"Of course I would like to make everyone happy, but it's not that easy."
She looked less than happy in the opening games as she was broken early by Amanmuradova and was twice just one point away from falling a double break behind.
There was a hint of ruthless arrogance in the way Sharapova dispatched Anastasia Rodionova, but Kvitova was edgy and almost diffident.
Her movement was poor and the mistakes were multiplying, but her superior power meant an upset never felt likely providing she could find her range.
At 4-1 down in the first set she finally started to put it all together and she won five games in a row to win the opening set and the second was more straightforward.
A rain delay threatened to cause the first appearance of the Wimbledon roof, but the giant mechanical structure was held back as the swift shower passed and Kvitova returned to court to finish off her opponent.
"It was lot of firsts for me today but I'm happy that I stayed calm inside and not to be panic in the important points," she said after setting up a second round clash against Britain's Elena Baltacha.
Deposed world number one Victoria Azarenka was untroubled against Irina Falconi in her match, screaming to a 6-1 6-4 victory while former French Open champion Francesca Schiavone, the 24th seed, survived a scare against home favourite Laura Robson before winning 2-6 6-2 6-4.