American Jeremy Wariner warmed up for the defence of his 400m world crown in Osaka later this month by storming to a new personal best in Stockholm.
Wariner believes he can run 43.30 seconds at the Worlds
The Olympic champion clocked 43.50 seconds to equal Quincy Watts as the third fastest man ever behind mentor Michael Johnson and Butch Reynolds.
"It feels great to go into the World Championships half a second faster than all the rest," Wariner, 23, said.
Britain's Michael Rimmer also set a new personal best as he won the 800m.
The 21-year-old from Liverpool clocked one minute 45.17 seconds to claim the biggest win of his career, edging out Dmitrijs Milkevics and Kenya's Richard Kiplagat.
Wariner was rewarded for his career-best mark, and a second stadium record in a row, with a one-carat diamond.
Normally, 10.04 is a joke - it was not a good race
Conditions were perfect at the DN Galan Super Grand Prix, where it was a cloudless, hot day.
"The weather was perfect," Wariner said. "If I run like this in Osaka, I can almost guarantee a 43.3 run."
World record holder Asafa Powell did not make the most of the conditions however, clocking 10.04 on his way to winning the 100m.
The Jamaican, who will head-to-head with Tyson Gay in Osaka, recovered from a poor start to edge out Derrick Atkins and Churandy Martina.
"Normally, 10.04 is a joke," said Powell. "It was not a good race. I got a bad start but I managed to accelerate and catch up.
"But I'm not worried about the World Championships, I know what I did wrong and it's easy to fix."
Rising British star Stephanie Twell recorded a personal best over 5,000m, clocking 15:47.53 for ninth place.
Germaine Mason finished fifth in the high jump with a best effort of 2.24m while 1500m specialist Andy Baddeley finished fifth place over 1,000m.