Ian Thorpe finally let a title escape his grasp but returned in full pomp to win a fifth gold medal and claim his fourth record of the week at the world championships in Fukuoka, Japan, yesterday.

Thorpe sealed Australia's victory in the 4 x 200 metres freestyle relay by pulverising the world record on the final leg and compatriot Geoff Huegill also claimed a world mark in the 50 metres butterfly.

Anthony Ervin ended Thorpe's golden run in the 18-year-old's weakest event, the 100 metres freestyle, and led the United States on a triple title spree which lifted them level with Australia on eight golds apiece with two days to go.

Ervin produced the biggest upset of the week by beating Olympic champion Pieter van den Hoogenband and relegating Thorpe to fourth in the 100.

However the shaky electronic timing system caused a few palpitations in the American camp by initially failing to show Ervin's victory on the scoreboard, placing the Dutchman first and giving no time for the American.

Aaron Peirsol and Maggie Bowen kept American spirits bubbling with excellent victories in the men's 200 metres backstroke and women's 200 individual medley but Thorpe, as so often, had the last word in the final event of a dramatic night.

After setting world records in the 200, 400 and 800 metres freestyle, Thorpe took over on the anchor leg of the 200 freestyle relay with a huge lead, but 0.73 seconds outside record schedule. He sliced down the final length to bring his team home 2.39 seconds inside the old Australian world mark.

"That we were able to take (nearly) three seconds off the record was pretty amazing," said Thorpe, whose fifth gold lifted him equal with Americans Jim Montgomery (1973) and Tracy Caulkins (1978), the most prolific winners at a single world championships.

"We pledged this race to the girls," he added. The Australian quartet were disqualified after finishing first in the women's 4x200 freestyle relay because one of the swimmers jumped into the pool before the last team had finished.

Giaan Rooney earlier brought Australia gold with an unexpected victory in the women's 200 metres freestyle in which 1996 Olympic gold medallist and defending champion Claudia Poll of Costa Rica finished out of the medals.

Seventeen-year-old Luo Xuejuan scooped her second breaststroke gold with a powerful swim in the inaugural 50 metres event after winning the 100 on Monday.