SABINE Lisicki did the unthinkable this afternoon as world number one and defending champion Serena Williams was sent tumbling out of Wimbledon.

It was always slated to be the American's toughest challenge yet, but few could have predicted the enthralling duel that would follow on Centre Court.

German Lisicki, priced by several bookmakers at 10/1 to win the last-16 clash, started with aplomb and became the first woman of the fortnight to take a set off Williams.

The five-time Wimbledon champion looked a shadow of her normal self but recovered to dominate the second set.

Lisicki's exuberance and exquisite play was not to be overcome, though.

In a thrilling decider, the world number 24 broke the reigning champions serve three times to edge through a 6-2 1-6 6-4 victor and end Williams incredible 34-match winning streak.

Meanwhile, Laura Robson's dream run came to an end as the British number one was overpowered by Estonian big-hitter Kaia Kanepi.

Robson went a break ahead early on, but Kanepi's power from the back of the court proved too much for the 19-year-old and she took the first set on a tie-break.

Robson lost her temper on a couple of occasions and it showed in her play as she succumbed to a 7-6 (8/6) 7-5 defeat, ending her hopes of becoming the first British woman to reach the quarter-finals of Wimbledon in 29 years.