SERENA WILLIAMS has been written off more times than a banana republic's national debt but in winning the Australian Open yesterday she proved that 25 is no age at which to condemn a seven-time Grand Slam champion to the history books.

Williams beat top-seed Maria Sharapova 6-1, 6-2 in just over an hour with a display of awesome power and self-belief to complete one of the most extraordinary comebacks in the history of women's tennis.

It was Williams' first title of any description since she won her second Australian Open crown here two years ago. Ranked No 81 in the world after playing only five tournaments in the previous 16 months, when injuries and a seeming lack of commitment to her sport left many believing that retirement was imminent, Williams became the lowest-ranked player to win a Grand Slam tournament for 29 years.

No wonder Williams was in tears at the end, particularly when she thanked her family and remembered her sister, Yetunde, who was shot dead four years ago in Compton, the troubled suburb of Los Angeles where Serena and her sister, Venus, learned to play the game.

"Most of all I would like to dedicate this win to my sister, who's not here, " Williams told the crowd, her voice cracking. "Her name is Yetunde. I just love her so much. I'll try not to get tearyeyed, but I said a couple of days ago that if I win this it's going to be for her. So thanks, Tunde."

Like Venus, who missed this tournament because of a wrist injury, Serena is a scrapper who never knows when she is beaten. Some will see her victory as evidence of the underlying weakness of women's tennis, but her return to the top - she will jump 67 places to No 14 in tomorrow's new rankings list - can only strengthen the game.

Williams, who will play in tournaments in Bangalore and Dubai next month, said she could hardly wait for the clay court season and was already looking forward to the French Open in May.

The roof was closed over Rod Laver Arena (for the fourth women's final in five years) to keep out the rain, but the sky fell in for Sharapova. In her previous 85 matches in Grand Slam tournaments the US Open champion had never suffered such a comprehensive defeat.

A measure of the quality of Williams' performance is the fact that Sharapova will return to No 1 in the world rankings tomorrow. The 19year-old Russian had gone into the final on the back of 13 successive wins in Grand Slam matches, and after a year in which she had claimed five titles and reached the semi-finals or better in 13 of her 15 tournaments.

Sharapova's serve creaked under the pressure of Williams' assault from the start. The Russian served six double faults, struggled with her ball toss and saw her second serves in particular dispatched with merciless force.

In contrast, Williams served beautifully. Her seven aces took her tournament tally to 64, 19 more than any other player and 29 more than Sharapova. What impressed on this occasion was not so much her power, but her placement: to keep the ball out of Sharapova's long reach is an achievement in itself.

It was a similar story with the two players' ground strokes. Sharapova never got into any sort of rhythm, while Williams was in the groove from the moment she hit a backhand cross-court winner on the first point.

The American went for her shots throughout, hitting 28 winners to Sharapova's 12.

Nor was it simply a matter of power, for Williams showed a deft touch whenever she approached the net.

Sharapova had the misfortune to meet Williams just as the American rediscovered her natural game. "I finally played it for the first time this whole tournament, " Williams said. "When I'm staying close to the baseline, I'm playing that way, aggressive. That's the way I was raised. My Mum and Dad taught me to play that game of tennis. For some reason, I stay on the baseline. But that was the Serena that I've been trying to showcase for years and years."