By Pritha Sarkar

LONDON (Reuters) - A time violation warning, a few spots of rain and the thunderous groundstrokes of her rival could not throw Venus Williams off her long-limbed stride as she reached the Wimbledon third round with a 7-5 4-6 6-3 win over Greek qualifier Maria Sakkari on Thursday.

Playing an opponent who was not even aged five when she won the first of her seven grand slam titles at Wimbledon in 2000, the 36-year-old Williams proved that it would take more than sheer determination to topple the American at her favorite tournament.

After two days of rain created a scheduling headache for the organizers, the five-times Wimbledon champion found herself cast adrift on Court 18 -- an arena once labeled "a parking lot" by former world number one Jelena Jankovic.

With only 782 seats available for punters, there was a constant tailback of spectators jostling for space in the narrow gangways as they stood eager to catch a glimpse of the oldest player in the women's draw.

The American eighth seed drew plenty of applause when she won the first set despite dropping serve in the seventh game after incurring a time violation warning for switching rackets between points.

Wimbledon debutante Sakkari, who grew up idolizing Williams's younger sister Serena, also drew shouts of "Bravo Maria" as her powerful groundstrokes started to hit their targets with more consistency.

However, Venus, who will contest her 300th grand slam match if she reaches round four, was in no mood to be upstaged by a 20-year-old.

Apart from defeat by unranked Kim Clijsters at the 2009 U.S. Open, Williams had not lost to a player ranked outside the world's top 100 at a grand slam this century.

While world number 115 Sakkari's hopes of ending that run gathered momentum when she broke Williams three times to bag the second set, Williams rediscovered her touch in the third set to book a last-32 meeting with Russian Daria Kasatkina.

(Reporting by Pritha Sarkar, editing by Ed Osmond and Clare Lovell)