Grant Hackett is so used to swimming alone that it's no surprise that his greatest competition is rarely in the pool at the same time as him.

His domination of long-distance swimming is such that his greatest rivals are the clock and the ghosts of races long ago.

Take Wednesday's 800 metres freestyle final at the world championship in Montreal when the race was as good as over when he opened up a body length's lead on the first lap.

But Hackett was still engaged in an epic battle to break Ian Thorpe's world record of seven minutes 39.16 seconds, which his compatriot set at the 2001 world championships in Japan [Images].

His tactics were clear: to go out as hard as he could then hang on grimly.

He raced through the first 100m in 54.38 seconds, faster than John Devitt swam to win the 100m gold medal at the 1960 Olympics [Images].

He reached the 200m in 1:51.89, almost a second quicker than Mark Spitz when he broke the 200m mark at the 1972 Munich Games.

Hackett's rivals were falling further and further behind but he kept up the pace. He reached the halfway mark in 3:47.17, faster than Joerg Hoffman swam to win the 400m as recently as the 1991 world championships.

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 in reserve to snatch the record by more than half a second -- stopping the clock at 7:38.65.

"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."

UNDISPUTED KING

Hackett is the undisputed king of long-distance swimming.

He is unbeaten over 1500m since 1996 and his world record of 14:34.56 is seven seconds faster than anyone else has ever swum.

He has, however, spent most of his career swimming in the shadow of Thorpe, who had beaten him in the 400m at the past three world championships and last year's Athens Olympics.

But Thorpe's decision to skip Montreal to recharge his batteries before the long road to Beijing [Images] has allowed Hackett to set down some markers of his own.

By winning the 400m, Hackett became the first person to win gold medals at four world championships. His second place in the 200m allowed him to pass Thorpe, Jenny Thompson and Michael Gross as the most prolific medal winner at the championships.

His victory on Wednesday allowed him to join Thorpe as the only swimmers to win six individual world titles, a record he should claim for himself when he contests the 1500m on Sunday.

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

"He's the most credible swimmer that we've had in history, and being one of his main rivals is a real honour.

"To break one of Ian's world records is always going to bring a lot of attention and I can understand that.

"I'm used to that, it's nothing new, but I feel like I've done enough to prove myself over nine years of international swimming."

Hackett had beaten the 800m world record twice before, at the 2001 Australian championships and again at Fukuoka, but neither counted because he finished behind Thorpe both times.

"It was a personal thing for me," 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 performance on Wednesday was all the more impressive because Larsen Jensen, who finished 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.

"I was thinking to myself 'he's so far ahead, damn I hope he's doing a world record'," said Jensen.