Six-time Olympic champion Usain Bolt dipped below 10 seconds to win the 100m in 9.87 at the Anniversary Games.
The Jamaican, who has been struggling for form and fitness, won both his heat and the final in the same time in wet conditions at the Olympic Stadium.
"I really wanted to run faster," said Bolt, 28, who defends his world title next month. "But it's getting there."
Meanwhile, Britain's double Olympic champion Mo Farah received a great reception as he won the 3,000m.
Farah, 32, was competing in England for the first time since allegations of doping were made against coach Albert Salazar, claims which Salazar and Farah deny.
Olympic heptathlon champion Jessica Ennis-Hill, returning to the scene of her greatest triumph, ran 12.79 in a world-class 100m hurdles – just 0.25secs off the personal best she set on this track three years ago.
On the weekend when she will decide whether to compete at next month's World Championships, the 29-year-old looks like she is finding her best form in her first season back since giving birth to her son, Reggie.
Besides Farah, other British winners on the night were 20-year-old Anguilla-born sprinter Zharnel Hughes, a member of Bolt's training group in Jamaica, who clocked an impressive personal best to win the 200m in 20.05, and Laura Weightman, who won the 1500m.
Bolt had only raced once over 100m in 2015 before Friday, recording a time of 10.12 in April, because of a pelvic problem.
But his times were season's bests and equal sixth-fastest times of the year over the distance, although they are still behind American Justin Gatlin's world-leading time of 9.74.
Competing on the track where he won three gold medals at London 2012, Bolt started poorly in the final but overpowered his rivals in the last 10m.
America's Michael Rodgers was 0.03secs behind in second, while Bolt's compatriot Kemar Bailey-Cole was third in a personal best 9.92.
Significantly, British 100m champion CJ Ujah ran under 10 seconds for the second time in his career, equalling his personal best 9.96 on a chilly London evening.
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