Usain Bolt got his farewell to athletics off to an inauspicious start at the IAAF World Championships, while Mo Farah continued his domination of the 10,000 metres.
Bolt's highly-anticipated appearance on the track for the 100m heats was far from one of his most convincing, the eight-time Olympic champion recovering from a poor start to win and advance to Saturday's semi-finals.
There was no such concerns for another man who typically shines on the big occasion. Farah produced a world-leading time of 28 minutes and 49.51 seconds to successfully defend his 10,000m title in front of an adoring home crowd.
Although there were no upsets in the women's 1500m, there was a shock in the men's long jump as Olympic champion Jeff Henderson failed to qualify for the final.
As one of sport's greatest stories began its final chapter, Bolt received a rapturous welcome to the track at London Stadium.
A rapid finish secured him a time of 10.07 seconds - the eighth fastest of the heats - but his reaction and comments in the aftermath proved he was far from impressed.
"I have to get my start together. I can't keep doing this because if I do this in the final it will be over. I have to get my improvement going," said Bolt.
Fellow Jamaican Yohan Blake advanced but failed to win his heat, while Julian Forte and Christian Coleman were the standout performers.
The opening night of the championships concluded with Farah's bid for glory in the 10,000m and the home nation's biggest star certainly did not disappoint.
Farah was certainly tested as his rivals set a harsh pace, but there were still familiar scenes in the closing 100m as the reigning champion kicked clear to beat Joshua Cheptegei and Paul Tanui.
Incredibly, Farah has now won 10 major global finals in succession, this latest triumph his third 10,000m World Championship victory to go with three over 5000m and four Olympic golds.
Farah can double up once again if he wins the 5000m final next week.
SHORT JUMP FOR HENDERSON
Jeff Henderson took gold at the Olympics at Rio 2016 but will not follow up that success with a world title.
The American leapt 8.28m in Sacramento in June and was unable to replicate that, his final jump of 7.84m not enough to put him in the frame for a tilt at the medals.
"It's not what I wanted at all, I wanted to do better but I guess it's harder to come back after last year," Henderson said in reference to winning in Rio.
"I'm kind of sad I didn't get to go out here and get where I wanted to, but I guess I'll take something from it for next time."
1500M HOPEFULS THROUGH
Defending champion and Olympic silver medallist Genzebe Dibaba looked more than comfortable as she hung on the back of Great Britain's Jessica Judd before pushing on to win the first women's 1500m heat.
Her time of four minutes and 2.67 seconds was the fastest of the night, with 800m specialist Caster Semenya following her home with a season's best.
World leader Sifan Hassan moved up from the back at the start of the final lap to overtake home favourite Laura Muir and finish first, while reigning Olympic champion Faith Kipyegon also advanced.
"The event is very strong with Sifan and Caster, so it will be a very fast race I think," Dibaba said, looking ahead to the potential final.