Yves Lampaert won stage one of the Tour de France as defending champion Tadej Pogacar took time out of his main rivals in the opening individual time trial in Copenhagen.
Lampaert rode superbly to negotiate the damp conditions and finish five seconds clear of fellow Belgian Wout van Aert.
Pogacar was a further two seconds back in third place, nine seconds ahead of Slovenian compatriot Primoz Roglic.
Britain’s Adam Yates and Geraint Thomas finished 13th and 18th.
Fellow Ineos Grenadiers rider Tom Pidcock was sandwiched between the pair after taking advantage of the more favourable later conditions to roll over the line in 15th.
Thomas’ mixed fortunes
Thomas, 36, who won the Tour in 2018, rode the stage in a gilet after forgetting to take it off before the start and lost 18 seconds over the first part of a flat but technical route around the Danish capital.
“That was the worst first half of a time trial I have ever done,” Thomas said.
“I wanted to start fairly conservatively power wise but everyone is telling you to go easy on the corners, there’s three weeks and not to crash.
“The first few corners I cornered like my wife and she hasn’t ridden a bike for 12 years. It was unbelievable and then I realised I still had my gilet on.
“When I went through the first time check and I was 18 seconds down I just took the pin out. I know I could have done a better ride so it is annoying.”
‘I’m just a farmer’s son from Belgium’
While the Welshman’s time was far from disastrous on another day he may have been closer to the favourites for the stage.
His Ineos team-mate and world time trial champion Filippo Ganna bettered Mathieu van der Poel’s early mark before seeing Van Aert and Pogacar immediately eclipse him.
And as the heavy rain began to subside Lampaert delivered a stunning performance to claim a surprise victory.
The 31-year-old, who was disqualified from the Tour of Belgium for barging Tim Wellens only two weeks ago, was in tears at the end as his first Tour victory was confirmed.
“My mind is exploding,” Lampaert said.
“I thought a top 10 would be great and now I beat all the best riders in the world. I’m just a farmer’s son from Belgium. To do this, I never expected it.
“The roads were really wet, the pot holes were full of water. I think I had the same conditions as the main favourites. Always in the corners I said, ‘Yves, go faster, trust in your tyres’.”
Stage one results
1. Yves Lampaert (Bel/Quick-Step Alpha Vinyl) 15min 17secs
2. Wout van Aert (Bel/Jumbo-Visma) +05secs
3. Tadaj Pogacar (Slo/UAE Team Emirates) +07secs
4. Filippo Ganna (Ita/Ineos Grenadiers) +10secs
5. Mathieu van der Poel (Ned/Alpecin-Fenix) +13secs
6. Mads Pedersen (Den/Trek-Segafredo) +15secs
7. Jonas Vingegaard (Den/Jumbo-Visma) Same time
8. Primoz Roglic (Slo/Jumbo-Visma) +16secs
9. Bauke Mollema (Ned/Trek-Segafredo) +17secs
10. Dylan Teuns (Bel/Bahrain Victorious) +20secs
Selected others
13. Adam Yates (GB/Ineos Grenadiers) +23secs
15. Tom Pidcock (GB/Ineos Grenadiers) +24secs
18. Geraint Thomas (GB/Ineos Grenadiers) +25secs
112. Chris Froome (GB/Israel-Premier Tech) +1min 16secs