Even when he's nowhere near his world record-breaking best, the world can't catch Ian Thorpe.

The Sydney swimmer won his tenth world title with an emphatic victory over Olympic champion Pieter van den Hoogenband in the 200m freestyle.

The 20-year-old Thorpe clocked 1m45.14s to be more than a second adrift of his own world mark set at the last world championships two years ago but he was still a body length ahead of the rest of the field.

It was another night of drama for Australia in Barcelona's Palau Sant Jordi pool with Leisel Jones and Matt Welsh both learning what a difference a day makes.

After setting a stunning world record in her 100m breaststroke semi-final, Jones experienced the downs of swimming's rollercoaster ride, having to settle for a bronze medal.

And Welsh, who turned his gaze heavenwards again after an unexpected gold and world record in the 50m butterfly, could manage only silver in his premier event, the 100m backstroke.

Thorpe's win was the lone gold medal for Australia on day three of competition.

Van den Hoogenband turned first at the 100m mark of their final in under world record pace but the Thorpedo brought in his trademark kick to sail past the Flying Dutchman and win by about a body length.

"It's good to race like that. I enjoy it when I get those opportunities," said Thorpe, who opened the meet with gold in the 400m freestyle.

"It was an average time but I'm pretty happy with the result."

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