Grant Hackett shattered Ian Thorpe's 800 metres freestyle record at the world championships on Wednesday to join his Australian rival as the only swimmers to win six individual world titles.

Hackett demolished his rivals to take gold in seven minutes 38.65 seconds, slashing more than half a second off the mark set by Thorpe at the 2001 world championships in Japan [Images], when the pair engaged in an epic battle.

"It's always a great feeling to break any world record but to break one of Ian Thorpe's is special because it has extra credibility," Hackett said.

"I already have the 1500m world record and I thought I really should have the 800m as well because it's in my range, it's really my forte."

Hackett's record took the spotlight away from Michael Phelps and overshadowed a remarkable performance by German doctor Mark Warnecke, who became the oldest world champion in history.

Warnecke turned back the clock to pull off a shock win in the men's 50m breaststroke final and claim a first world title at 35, an age when most top swimmers have long retired.

The oldest world champion before him was Russian Alexander Popov, who won the freestyle sprint double in Barcelona two years ago at 31.

"People have been asking me for 15 years when am I going to quit," smiled Warnecke, whose previous best result was the 50m breaststroke title at the 2000 European championships.

"I don't know, maybe another 20 years. Why not?"

Solenne Figues provided France [Images] with their second gold of the championships when she timed her burst to perfection to win the 200m freestyle while Pawel Korzeniowski of Poland took full advantage of Phelps's absence from the 200m butterfly with an all-the-way victory.

Phelps elected to bypass his favourite event to experiment with a punishing new programme that saw him required to swim two semi-finals in 75 minutes on Wednesday.

He qualified fifth fastest for Thursday's 100m freestyle final in a personal best of 48.93, half a second behind South African Roland Schoeman, then was second quickest behind his American team mate Ryan Lochte in the 200m individual medley.

"I'm used to doing multiple races every day," Phelps said. "I wouldn't say it's a piece of cake...but this is what I grew up doing."

CRACKING PACE

But none of their performances came close to the astonishing display by Hackett, who produced one of the finest displays of endurance swimming ever.

The 25-year-old law student made his intentions clear from the outset when he set out at a cracking pace, opening up a full body length's lead over his rivals.

He surged further in front after each lap and was more than five seconds ahead of Thorpe's old mark with 200m to go.

He was still 3.82 under with 100m to go and although his blistering early speed was starting to take its toll, he had enough stamina in reserve to snatch the record.

"I knew I had to be well under to have a chance because I am never going to come home as fast as Ian," Hackett said.

"I think I probably swam a perfect race tonight."

Hackett's performance was all the more impressive because Larsen Jensen, who finished a distant second in 7:45.63, sliced two seconds off the American record while Russia's [Images] Yuri Prilukov set a European record to take third in 7:46.64.

Hackett's victory added to his already staggering list of achievements. He is the only swimmer to win gold medals at four world championships and he and Thorpe are the only swimmers to have won six individual career titles.

Hackett also holds the record for most career medals (15) with the likelihood of more to come in the 4x200m freestyle relay and the 1500m, his favourite event.

Apart from the world record he is unbeaten over the distance in almost a decade, winning the past three world titles and two Olympic golds.

Warnecke took gold in the breaststroke in a time of 27.63 seconds. Mark Gangloff of the US was second in 27.71 while Kosuke Kitajima of Japan was third in 27.78.

LATE BURST

Figues took the women's 200m freestyle gold in 1:58.60 ahead of Federica Pellegrini of Italy [Images], China's Yang Yu and Sweden's Josefin Lillhage dead-heated for third in 1:59.08.

Pellegrini led the field through the first three laps but Figues moved to third on the turn for home then inched her way to the front. Her compatriot Laure Manaudou won the women's 400m freestyle on Sunday.

Korzeniowski led all the way to take the 200m butterfly title in 1:55.02 seconds, more than a second outside Phelps's world record. Japan's Takeshi Matsuda finished second in 1:55.62 while China's Wu Peng was third in 1:56.50.