Venus Williams may have taken to wearing a mock tiara on court but she still has some way to go before she is crowned champion here.

Williams, who beat the 1999 finalist Amelie Mauresmo 6-2, 3-6, 6-3 to secure a place in the quarter-finals yesterday, has enough nous beneath that sparkling headband to know that life only gets harder from here on in.

With a quarter-final against Amanda Coetzer next, and a semi versus either her sister Serena or Martina Hingis in prospect, Williams must tighten up her game if she is to maintain her winning run in the Grand Slams.

Against Mauresmo she was generous to a fault, serving at a fraction of her usual speed and spraying shots far and wide as though aiming for the cheap seats. Not that Mauresmo was much better. The Frenchwoman hits the ball nearly as hard as Williams, but just as often hit it out yesterday.

The Williams's obstacle in the quarters will be the small but perfectly formed Coetzer, who beat the Argentine Paola Suarez 6-1, 6-4. Coetzer, as she often does, has crept through the draw unnoticed by almost everyone. At 5 ft 2 in that is not hard but she packs a lot in to that small frame, including extraordinary stamina, lightning speed and an unquenchable will to win.

It is years since the South African last reached the semi-finals of a grand slam, the 1997 French Open, and at 29 she must feel this is about her last chance to win a major, even if she has to beat someone nearly a foot taller to do it.

Martina Hingis must sympathise with Coetzer. She too finds herself surrounded by women bigger and stronger than her and this tournament is no exception. Hingis will take on Serena Williams in the quarter-finals after both scored fluent wins yesterday but, scarily for Hingis, the younger Williams is the easiest of the three scalps she will probably have to take if she is to recapture this title.

Hingis notched up another easy win to add to her collection here by beating Italy's Rita Grande 6-0, 6-3, while Williams took care of the Czech Daja Bedanova 6-2, 6-2.

Hingis has sought in her first four matches to use the minimum of energy to ensure she will have enough left in the tank for the big three of Williams, Williams and Davenport.

Now, she says, she is as ready as she will ever be. "Beating them all in one event, it's quite difficult," she agreed, in something of an understatement, "but nothing's impossible."

At least Hingis only has to worry about her opponents. Anna Kournikova must wonder what her more obsessive fans - or perhaps that should be "followers" - will try next after a smoke flare was thrown from the crowd on to the court where she was playing doubles.

Kournikova, playing with Barbara Schett against Shinobu Asagoe and Yuka Yoshida, was preparing to receive serve when the flare, billowing orange smoke, landed a few feet away from her. Play was held up for 12 minutes while an official painted over a scorch mark left on the court and Kournikova and Schett won 2-6, 6-3, 6-3. A 15year-old boy was cautioned by police.

Britain's interest in the men's competition was ended when Greg Rusedski went the way of compatriot Tim Henman, losing 6-3, 6-2, 7-5 to France's Arnaud Clement. The 23-year-old Frenchman referred to yesterday's opening sets in French slang as being like a butcher's shop, with Rusedski chopped and strung up like prime beef: "I could not understand why he served like that. I was under no real pressure at all."

Rusedski offered this explanation: "I was hoping I could slide the ball around, but I didn't have the rhythm." He had previously indicated, given the changes made in his service action to ease the stress on his injured back, that there would be off-days. When, in the third set, he tried to increase the tempo, Clement responded with a series of flashing returns. "And you can't do much about that," Rusedski said.

Clement now plays Yevgeny Kafelnikov, at number five the highest seed remaining, for a place in the semi-finals, the Russian having defeated Sweden's highly promising 19year-old left-hander Andreas Vinciguerra - his father is Italian - in straight sets.

Tomorrow's other quarterfinal will feature a second Frenchman, Sebastien Grosjean, who knocked out Norman, the number four seed and a semi-finalist last year.

Norman lost 7-6, 6-3, 0-6, 6-4 but won himself some new friends with an unusual act of sportsmanship. The Swede conceded match point to Grosjean despite the fact that a let had been called on what both men believed to be an ace from the Frenchman.

Neither player heard the call of let from the umpire Mike Morrissey and, while Grosjean celebrated, the umpire was forced to come down from his chair to insist he take the serve again. Norman, though, shook his head and offered his hand in concession, earning a huge roar of appreciation from the crowd and a sigh of relief from his opponent.

Norman spent much of the contest querying line-calls and arguing with Morrissey, yet when it came to the biggest point of all he listened to his conscience.

"We play for a lot of money, we play for a lot of points," said Norman, "but when I grew up my mother always told me to never give up but to always play by the rules. I think my mother will be proud of me when I call her tonight."

Grosjean now plays Spain's Carlos Moya, a former French Open champion and beaten finalist here in 1997.