Mo Farah became the first Briton to run the 5,000m in under 13 minutes at the Diamond League meeting in Zurich but could only finish fifth in his race.
Farah broke David Moorcroft's 28-year-old British record of 13 minutes 00.41 seconds, finishing in 12:57.94 in a race won by Ethiopia's Tariku Bekele.
European 5,000m and 10,000m champion Farah said: "I have been waiting for so long for this. I am over the moon."
Meanwhile, American Allyson Felix won the 400m Diamond League crown.
Farah became the first Briton to win both the 5,000 and 10,000 metres gold medals at the European Championships when he triumphed in Barcelona three weeks ago and the 27-year-old was again in fine form in Zurich.
"For the last four years its been there and there about," said Farah after breaking the British record.
"I knew it would come soon but I didn't know how soon.
"To go under 13 minutes is an awesome feeling. When David Moorcroft ran that time, it was a world record, so that shows you how much athletics has moved forward."
Moorcroft, who set his mark at the Bislett Games in Oslo in 1982, said he was excited by Farah's potential.
"It was amazing what he did tonight. It was a great run and to do it after his double win in Barcelona was a great run," said Moorcroft.
"To do it after the season's major championships, it is a really physically and emotionally hard time of the season to produce your best, and for him to do it now is really special.
"I think he's probably the most talented runner we've had in distance running.
"I think people really want to see him win something at world or Olympic level, and that would be some achievement."
Ending in Brussels on 27 August, the Diamond League is a 14-date global series giving season-long winners the right to be called world number one.
Felix added the 400m success to her 200m title with a convincing victory over the world indoor champion Debbie Dunn in a time of 50.37 seconds.
Despite the win, Felix said she was disappointed at not breaking the 50-second mark.
"The times weren't there," she told BBC Sport. "It's a new event for me and I just had a go at it.
"I have potential [in the 400m] but also a lot of work to do. I'm encouraged, but I have to drop those times next year though."
A US quartet featuring Tyson Gay ran the fourth-fastest time ever in the 4x100m relay.
Trell Kimmons teamed up with Gay, newly-crowned Diamond League 200m champion Wallace Spearmon and Michael Rodgers to clock a meet record of 37.45 seconds.
Only Jamaica, in winning gold at the 2008 Beijing Olympics, and two previous US teams - in Barcelona and Stuttgart in 1992 and 1993 - have gone faster.
"It was a lot of fun, one of the funniest moments of the season for me," said Gay, who had opted not to compete in the 200m.
With world record holder Usain Bolt missing because of a back injury, Spearmon took the spotlight in that race with a meet record time - and his season's best - of 19.79 seconds.
Fellow American Jeremy Wariner ran the world's fastest 400m time of the year with 44.13 seconds, winning the overall Diamond League title by some margin.
His compatriot David Oliver failed in his latest attempt to break Cuban Dayron Robles' 110 hurdles world record of 12.87 seconds after stumbling over the line in 12.93 - four hundredths of a second outside his national record set in Paris last month.
"I know I'm not the perfect hurdler," said the Diamond League champion. "That's why I'm missing the world record."
There was further success for the United States in the field, Dwight Phillips and Brittney Reese winning the men and women's long jump events respectively.
The Weltklasse meet, or the "Olympics-in-a-day" as it is sometimes known, was missing some of track and field's biggest stars despite crowning champions in 16 events.
The remaining 16 discipline finals are decided in Brussels.
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