World record holder Wayde van Niekerk ran the fastest 400m time of the year on his return to action at the Diamond League meeting in Lausanne.
In his first international 400m since breaking the world record in the 2016 Olympic final, the 24-year-old South African won in 43.62 seconds.
It beat Michael Johnson’s record at this meeting of 43.66, set in 1996.
Britain’s Laura Muir, 24, ran a personal best of one minute 58.69 seconds to finish fifth in the 800m.
Compatriot Lynsey Sharp, 26, set a season’s best of 1:58:80 to finish seventh in a race won by Burundi’s Francine Niyonsaba in 1:56.82.
Scot Muir, who has recently recovered from a stress fracture in a foot, said: “You do not realise the value of something until it is taken away from you.”
Eilidh Doyle, 30, ran a season’s best 54.36 in finishing third the 400m hurdles.
Fellow Britain James Dasaolu, 29, was fifth in the 100m in 10.12 as 35-year-old American Justin Gatlin won in 9.96.