Chakvetadze, 20, has admitted she often struggles to keep her composure during key moments and she was unable to stay cool as Dutch teenager Krajicek won their third round match 7-6 (8/6), 6-7 (5/7), 6-2.

The Russian wept on court after allowing Agnes Szavay to take a set off her at the French Open this year and that volatile temperament failed her again against Krajicek, the sister of former Wimbledon champion Richard.

Chakvetadze's talent has never been in question and she has enjoyed a meteoric rise to a career high seventh in the world rankings on the back of quarterfinals appearances at the Australian and French Opens this year.

But, after winning a tense second set tie-break to level the match against Krajicek, she let a position of dominance slip away.

The Muscovite couldn't maintain her poise when it came to the crunch. She lost concentration and, with the tears welling up once more, was broken at the start of the deciding set.

Chakvetadze was growing increasingly frustrated and when she failed to convert a break point in the seventh game, Krajicek served out her impressive victory.

Justine Henin's bid to win Wimbledon for the first time remained on course as she advanced to the fourth round with a crushing victory over Elena Vesnina.

The world number one eased past the unseeded Russian, winning 6-1, 6-3, and now faces either 15th seed Patty Schnyder or Ukraine's Alona Bondarenko for a place in the quarterfinals.

Wimbledon is the last unconquered frontier for Henin. The Belgian has savoured Grand Slam glory at the French, Australian and US Opens, but success on the grass courts of south-west London has been tantalisingly out of reach.

Henin lost in the 2001 final to Venus Williams and fell at the final hurdle again last year against Amelie Mauresmo.

But the reigning French Open champion has the game to win at the All England Club. She strolled through her first two matches with the minimum fuss and she was in charge immediately against Vesnina. In another game, Switzerland's 15th seed Patty Schnyder beat Alona Bondarenko of Ukraine 6-4, 3-6, 8-6.

Earlier, Wimbledon police chiefs have altered their security plan for the championships following Friday's defusing of a car bomb in the heart of London's theatre district.

Superintendent Peter Dobson, in charge of the police operation at the All England Club, said that, while there had been no specific threat to Wimbledon, security measures at the Championships had been fine-tuned in the wake of the incident.

"Whilst I have made some adjustments to the security of the perimeter, with some police officers being redeployed from inside, and some enhanced checking of vehicles entering the car parks, the security plan remains commensurate to the threat," Dobson said.

"There is no intelligence that increases the threat to the championships. My message is for all persons attending to remain vigilant and to report anything suspicious to the police.

"This is a timely reminder that we live in dangerous times and our top priority will always remain the safety of the public."

The new plan means more vehicle interiors are being checked and there is a higher police presence around the edge of the club, which is bordered by busy roads, a golf course and suburban housing.

Amid widespread disruption in city, new Prime Minister Gordon Brown warned that the alert was a fresh warning of the threat faced by Britain, which soon marks the second anniversary of the London suicide attacks which killed 52 people.