Ian Thorpe tonight added world record number two to his long list of extraordinary swimming achievemnents when he took 4.41 seconds off Kieren Perkins seven-year-old world record for 800 metres freestyle in Hobart.

"The Thorpedo" launched his size 17s into full throttle and took off with 125 metres to go to clock a time of 7:41.59 secs in a stunning performance at the Tattersall's Hobart Aquatic Centre.

Thorpe and Hackett swam stroke for stroke for almost 700 metres, before the world record holder and Olympic champion for 400 metres, took off in an awesome display of power.

Hackett had no answer to Thorpe's amazing surge - but he too clocked a time under Perkins world mark of 7:46.00, set on the way to his 1994 world mark for 1500m at the Commonwealth Games in Canada.

The 20-year-old Olympic 1500m champion from Miami finished a gallant second in 7:44.57, with his training partner, Stephen Penfold third in 8:04.55.

But it was Thorpe's night and he kept the crowd and an Australia-wide live TV and radio audience in suspense when he crusied through the first 700 metres - only approaching world record pace with 100 metres to go.

Thorpe actually negative split the race, swimming the first 400m in 3:52.27 and the second 400m in 3:49.32.

His splits were: 56.14; 1:55.06; 2:53.59; 3:52.27; 4:51.42; 5:50.58; 6:47.88 and 7:41.59.

Thorpe's final 100 metres was an amazing 53.71 - compared to Perkins' final 100m of 58.28.

(In Perkins defence he did then touch the wall with his feet and kept swimming to clock the 1500 metres freestyle world record of 14:41.66).

It was the second time Hackett has gone under a world record but finished second to Thorpe - the first time when the pair smashed the 400m short course world mark in Perth in 1998.

Thorpe admitted he still sees himself as a sprinter and Hackett admitted he wants to convince his mate stop at 800 metres.

"I don't want him to swim that extra 700 metres, no way," said Hackett.

And Thorpe gave Hackett a reassurance it wouldn't happen...not for a while anyway.

"Grant can feel safe for the time being, I won't rule out swimming the 1500 metres completely but I can't see myself doing it in the near future," said Thorpe.

Thorpe has now won the 400 and 800 metres at these championships and will chase the 200 metres tomorrow night and then a place in the 100 metres later in the week.

The other winners tonight were: Simon Cowley, who burried the ghosts of his 2000 Olympic Trials when he won the 100m breaststroke final (1:01.96); Olympic bronze medallist Justin Norris in the 200 metres butterfly (1:57.70) and Olympic relay silver medallist Dyana Calub in a new Commonwealth and Australian record time of 28.68 in the 50 metres backstroke.

Cowley's comeback to beat Olympic relay silver medallist and training partner Regan Harrison was a personal triumph and one he dedicated to his family for their support in helping rebuild his career.

Norris' victory proved a coaching triumph for mild-mannered AIS head coach Mark Regan, who coached Petria Thomas to the womens 200m butterfly title the night before.

It could well be a case of one door closing and another one opening for Regan, who is on the short list for one of Australian Swimming's new coaching appointments, expected to be announced in Hobart on Friday.

Paralympic star, Siobhan Paton, added gold medal number two in the 50m butterfly while Ben Austin won his second gold in the mens event.

Wednesday night's action will see Ian Thorpe back in the pool in the 200 metres freestyle and Leisel Jones chasing the women's breaststroke double in the 200m.