Serena Williams of the US returns to Serbia's Jelena Jankovic
Wimbledon champions Roger Federer and Serena Williams took contrasting routes into the second round on the opening day of the Olympic tournament at a revamped All England Club on Saturday.
While Serena produced a polished display in a brutal 6-3, 6-1 demolition of Serbia's Jelena Jankovic, Federer was made to sweat before finally beating Colombia's Alejandro Falla 6-3, 5-7, 6-3 on Centre Court a few hours later.
Federer appeared to be cruising to victory in his first match since defeating Andy Murray to win a record-equalling seventh Wimbledon crown.
But the world number one allowed Falla back into the match after wasting three match points in the second set and was pushed hard by the world number 51 in the decider before sealing a tougher than expected win on his fifth match point.
Two years ago, Federer had to come back from two sets to love down to beat Falla in the Wimbledon first round.
Federer will face France's Julien Benneteau in the last 32 in a rematch of their third round clash at this year's Wimbledon when the 30-year-old Swiss star again had to come from two sets down to win.
"It's great coming back (after winning Wimbledon), but it's so much harder to do it again in the first round knowing that every match for me is like a final. I'm really relieved and hoping to keep it up," Federer said.
It was much easier for five-time Wimbledon winner Serena, who was cheered on from the players' box by US First Lady Michelle Obama.
Williams ended a two-year Grand Slam title drought with her Wimbledon final victory over Agnieszka Radwanska 21 days ago and the American fourth seed, who plays Urszula Radwanska in the second round, looks in the mood to add Olympic singles gold to the two doubles titles she won with sister Venus.
"It was great seeing Michelle there," Serena said. "It just made me want to play better and I felt even better."
The genteel surroundings of Wimbledon have a well-earned reputation for a rather sedate atmosphere, but there was a sense the famous old venue has let its hair down for the Olympics, which are back in south-west London for the first time since 1908.
A concert by British band the Pet Shop Boys on Henman Hill opened the event, and all the courts were decked out in the purple Olympic livery, while players were allowed to break the Wimbledon tradition of wearing all-white and instead donned the colours of their nations.
Former Wimbledon finalist Tomas Berdych was the first big name to tumble in the men's singles as the Czech sixth seed lost 6-4, 6-4 to Steve Darcis, an unheralded Belgian ranked 75th in the world.
"It's an amazing feeling," Darcis said. "When you're young you watch Pete Sampras playing on Centre Court and you think maybe one day. Today it was my day. I played a great match."
Serbia's Janko Tipsarevic defeated former Wimbledon finalist David Nalbandian of Argentina 6-3, 6-4, while John Isner, the 6ft 9in American 10th seed, won his little and large battle with Olivier Rochus, defeating the 5ft 6in Belgian 7-6 (7/1), 6-4.
In the women's singles, Belgium's Kim Clijsters enjoyed her first taste of the Olympics as the four-time Grand Slam champion moved into the second round with a 6-1, 6-4 win over Italy's Roberta Vinci.
The 29-year-old next faces world number 45 Carla Navarro Suarez of Spain, who enjoyed a shock 3-6, 7-5, 10-8 victory over Australian fifth seed Samantha Stosur.
Petra Kvitova, the 2011 Wimbledon champion, had to dig deep to defeat Ukraine's Kateryna Bondarenko 6-4, 5-7, 6-4, while former world number one Caroline Wozniacki battled back to beat Britain's Anne Keothavong 4-6, 6-3, 6-2.
But Chinese 10th seed Li Na slumped out, losing 6-2, 3-6, 6-3 against Slovakia's Daniela Hantuchova.