Serena Williams wasted little time in seeing off Japan's Kimiko Date-Krumm after their third-round match was moved under the Centre Court roof with the light fading at Wimbledon.
The world number one and defending champion powered through 6-2 6-0 in 61 minutes to reach the last 16.
At 42, Krumm was the oldest woman ever to reach the third round at Wimbledon.
Their match had been scheduled for Court One, but with the time approaching 20:30 BST they were moved to Centre, where the roof guaranteed they would be able to finish.
Williams, 31, was surprisingly broken when serving for the first set, to the delight of the Centre Court crowd who wanted a contest in their unexpected bonus match.
The American was not in a charitable mood, however, and responded in kind to take the set before racing through the second to claim her 600th career win.
"That's awesome," she told BBC Sport. "I had absolutely no idea. That feels really good. On Centre Court - what better place to win 600 matches?"
Krumm, who lost to Steffi Graf in the 1996 semi-finals, did at least make one of her targets by keeping the five-time champion on court for over an hour.
"I'm finally starting to feel a little better," Williams added.
"I had such a long clay-court season and my first match I felt was a little awkward, so I'm getting there. I always like to peak towards the end."
She added: "It's unbelievable playing here on Centre Court under the roof - I don't think it gets better for me than playing under a closed roof on grass."
Williams will next face Germany's 23rd seed Sabine Lisicki, who beat number 14 seed Sam Stosur of Australia 4-6 6-2 6-1.
Eighth seed Petra Kvitova remains the highest-ranked player in the opposite half of the draw, after beating Ekaterina Makarova in a rain-delayed match.
The Czech, who won the title in 2011, had lost the second set and was a break down when rain stopped play on Friday.
She eventually won 6-3 2-6 6-3 against the number 25 seed to set up a meeting with Spain's Carla Suarez Navarro.
"I should go for every point and play my game," Kvitova said. "I played quite aggressively. That was the key."
Fourth seed Agnieszka Radwanska had to battle hard to beat 18-year-old American Madison Keys 7-5 4-6 6-3.
World number 52 Keys had already defeated Briton Heather Watson and number 30 seed Mona Barthel but, despite fighting back to take the second set, was eventually seen off by the 24-year-old Pole.
Radwanska, who lost to Williams in last year's final, will now face world number 72 Tsvetana Pironkova after the Bulgarian beat Petra Martic of Croatia 6-1 4-6 6-2.
Sixth seed Li Na she was made to work for her 4-6 6-0 8-6 victory over 32nd seed Klara Zakopalova.
Number 17 seed Sloane Stephens is also through following the completion of her match with Czech Petra Cetkovska, another that was carried over from Friday.
The 20-year-old American won 7-6 (7-3) 0-6 6-4 to reach the fourth round for the first time.
She will now face Monica Puig, after the Puerto Rican edged past Eva Birnerova of the Czech Republic 4-6 6-3 6-4.