Keely Hodgkinson, the Olympic 800m champion, ran a personal best at the Diamond League in Stockholm but was stunned by Audrey Werro, who won in a time of 1:53.98 seconds, the third-fastest women's 800m time ever and the fastest in the world this year.
Hodgkinson, competing in her first outdoor 800m race of the season, was narrowly behind in a British record of 1:54:33, while American Roisin Willis was third in 1:57:56.
The 22-year-old Werro set the pace during a first lap of 55.54 seconds and although Hodgkinson hit the front with 300m remaining, Werro cruised past her just after they turned onto the home straight.
"It was a quick one, a really interesting race," said Hodgkinson. "When Audrey went off I was like 'just chill', but massive respect to her. That was a great race and it will motivate me more in training to make sure that doesn't happen again."
Hodgkinson finished seventh in a rare outing over 400m on Thursday and plans to compete over 800m in Eugene before the Diamond League meeting in London on 18 July.
"I was a little bit apprehensive coming in, not quite knowing exactly where I was with the 800m, because we have been doing some 400 training and are going to put together the 800m now," she added. "But it makes me excited because I can build on this great start. It's still very early. It's good to have a run in your legs because you can learn what you can do better but overall I am quite happy with that race because I made the right decisions, but Audrey was just better on the day."
Meanwhile, Olympic and world champion Armand Duplantis suffered his first Diamond League defeat in three years. In March, the 26-year-old broke the world record for the 15th time, with a jump of 6.31m slightly north of Stockholm in Uppsala. But the best he could muster on Sunday was 5.80m, second to Australia's Kurtis Marschall (5.90m).
"I felt I was pretty unfocused, not ready to compete at the top level," said Duplantis, who is getting married next week. "I feel bad for my fans and family but I am not that mad. We have a saying in Sweden that says you are either lucky in games or in love, and in some strange way I think there's some message or silver lining in this that says something about the commitment that I am about to make in my marriage."
There was one local win in the men's discus for Daniel Stahl, with the world champion's throw of 69.60m beating Australia's Matthew Denny (69.02) and Slovenia's Kristjan Ceh (67.67). Britain's Lawrence Okoye was eighth with 64.02, some way short of his season's best (71.88).
In the women's 100m, Britain's Amy Hunt ran a personal best 10.97 seconds to finish second to America's Melissa Jefferson-Wooden. Dina Asher-Smith was sixth in 11.24. British sprinter Jeremiah Azu was disqualified after a false start in the men's 200m, which was won by American Kenneth Bednarek in 19.87 seconds, with South Africa's Sinesipho Dambile second in 20.10.
GB's Elise Thorner was second in the women's 3000m steeplechase, finishing almost 12 seconds behind Tunisia's
