Usain Bolt branded his start "horrifying" as sport's coolest customer admitted to feeling nervous on his return to the Olympic Stadium.
The Jamaican was back at the scene of his triple London 2012 triumph as a bumper crowd revelled in a party atmosphere, but he was made to sweat before blasting through to take the victory in the 100 metres.
The 26-year-old's time of 9.85 seconds was a season's best and the second fastest in the world this year after Tyson Gay, who is under a doping cloud - but it could have been a different story after he was almost left in the blocks.
He entered the arena atop a missile for his customary lap of honour before the action, but this run hardly fired out a major statement of intent ahead of next month's World Championships.
Bolt said: "It (the start) was horrifying for me. I think it is just race rust and I just need to get a few races in. The rounds in the World Championships will help that and get my legs freer and a bit lighter.
"Hopefully the coach (Glen Mills) will figure out what I need to do to get me more explosive out of the blocks."
The Jamaican still ran out a convincing winner, with American Mike Rodgers second in 9.98secs, but his time was still relatively sluggish by his own stratospheric standards.
Not that that bothered the capacity 60,000 crowd in east London as they re-lived London 2012 one year on for the first of the three-day Sainsbury's Anniversary Games.
Flashbulbs galore and a roar to rival those heard at the Olympics greeted Bolt when he was introduced to the crowd ahead of the race.
Earlier he had received the usual hero's welcome when he arrived at the start of the evening, posing, dancing and saluting the crowd as he completed a circuit of the stadium on a rocket, complete with Jamaican flag.
He said: "For the first time I think in a long while I was slightly nervous.
"Initially I was excited to come out because I knew it was going to be a big crowd, but when I got out there and I saw that it was ram-packed and the energy was still like the Olympics.
"It was just wonderful so I was slightly nervous, but I loved the energy of the crowd. It was beautiful and I love competing here."
He acknowledged, however, that he simply could not get away with such a poor start at the World Championships in Moscow.
"My mindset in a championship is always different and in a great field I would have probably been fifth or something," said Bolt, who said his rocket ride was "more scary than anything else".
The feel-good factor of last summer was in full evidence around the Olympic Park beforehand as fans kitted out in London 2012 gear assembled in the sun.
People had queued up at the gates from the afternoon in the forlorn hope of getting tickets, with the stadium long since sold out for the event.
Ever the showman, Bolt performed a lap of honour for his adoring fans at the end, even throwing his spikes into the crowd.
After all, this was the world's fastest man's first appearance on these shores outside of the Olympics since 2009, with Chancellor George Osborne granting a one-off exemption for overseas athletes taking part.
Asked if he could be back, Bolt said: "Hopefully, but that is up to the tax people."
This was also a chance to put the focus firmly on the athletics following the doping scandal which has rocked the sport, with Asafa Powell as well as Gay testing positive.
Bolt was grilled on the topic at yesterday's press conference, and forced to defend his own record-breaking achievements, but one day on and Bolt was able to concentrate on the day job.
"I try to assist the sport to do great things and to sport the sport in to a good light," he said.
"I am just here to do my best and to prove to the world that it is possible to run clean and train hard and be focused."
Great Britain's newest sprint star James Dasaolu was unable to test himself against the world's fastest man. The man who ran 9.91s in Birmingham earlier this month had to withdraw as a precaution after feeling a tight hip flexor in the warm-up.
It was a worrying development with the World Championships little more than two weeks away and must make him a doubt for the 4x100m relay tomorrow.
In his absence Dwain Chambers led the British 100m charge and came fifth in 10.10.
He said: "It was amazing being back here again, that was like my Olympic final.
"Tonight has given the sport what it needs - some excitement."
Other highlights of the meeting included an unsuccessful world record attempt by Ukrainian high jumper Bohdan Bondarenko, who failed his two efforts at 2.47 with the competition already won.
Great Britain's 4x100m women's relay team raced to the fastest time by a British women's quartet in 12 years to claim an impressive victory.
Britain's women did not even qualify a team for last summer's Games, but tonight's line-up of Dina Asher-Smith, Anyika Onuora, Annabelle Lewis and Ashleigh Nelson won convincingly in 42.69.
Grenadian Olympic champion Kirani James won the 400m in 44.65, while Bolt's compatriot Warren Weir, the Olympic bronze medallist, won the 200m in 19.89.