Insatiable distance champion Grant Hackett is renowned as being a glutton for punishment.

But it is the rest of the competition feeling the pain at this week's world championship swimming trials as the re-energised Queenslander gobbles up his opposition.

The lanky 24-year-old motored to his third freestyle title of the week by winning the 800m freestyle in a canter in seven minutes and 43.16 seconds in Sydney.

He was four seconds off Ian Thorpe's world record and led the Gold Coast's Miami club to the top four places with Canadian-turned-Australian Kurtis MacGillivary booking a flight to his former home country in July.

1500m master Hackett now needs only to win his pet event on Saturday night to become the first man to win four Australian freestyle titles since Olympic bronze medallist Justin Lemberg in 1984.

Hackett's struggle to win the 1500m at last year's Athens Games had many believing it was only a matter of time before American Larsen Jensen or Welshman David Davies ended the superstar's nine-year reign in the event.

However Hackett is swimming as well as ever after recovering from his well-publicised health problems last year.

He said he was really looking forward to the 1500m and that lowering his world record of 14.34.56s set at the 2001 world championships was not out of the question in Montreal.

"I would not say at this stage, but at world championships it is probably not that unrealistic if I had a good preparation," Hackett said.

He comfortably won the 200m and 400m national titles in Ian Thorpe's absence this week and the Thorpedo's no-show has not slowed down the dual Olympic gold medallist.

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