Julian Alaphilippe sprang a superb late attack to win stage one of the Tour de France after two huge crashes in the closing stages.
The 2020 runner-up Primoz Roglic and Britain’s Chris Froome were among those to fall in two separate incidents in the final 45km.
In the first, a fan holding a placard sparked the first mass pile-up – with organiser ASO saying it will now sue as a result.
Froome’s crash came 8km from the end.
He was among the worst affected when more than 50 riders came to grief, the four-time Tour winner gingerly getting back on his saddle and crossing the line over 14 minutes down.
His Israel Start-Up Nation team later confirmed that scans showed no fractures, but an update on whether he would continue in the race would come on Sunday, they said.
On Sunday, Froome tweeted a thumbs up picture of himself and a message saying “ready for round two”.
The 197.8km run from Brest to Landerneau had been uneventful until the crashes. Both caused severe disruptions to the race, the first coming when Jumbo-Visma’s German rider Tony Martin was sent tumbling near the front of the main bunch, causing chaos behind him with riders and bikes strewn across the asphalt.
It took almost a full 25 kilometres for a bloodied and bruised peloton to fully regroup, with DSM’s German rider Jasha Sutterlin becoming the first to abandon the race.
“We are suing this woman who behaved so badly,” Tour deputy director Pierre-Yves Thouault told reporters, before that was confirmed to BBC Sport by organiser ASO.
“We are doing this so that the tiny minority of people who do this don’t spoil the show for everyone,” he added.
Overall contenders Tao Geoghegan Hart of Britain, as well as Colombian Miguel Angel Lopez, were among the riders to be held up before a second crash, this time at high speed on a descent before the climb up the Fosse-aux-Loups, ripped through the peloton again.
It was also hardly an ideal opening day for Ineos Grenadiers, with Richie Porte losing more than two minutes and Geoghegan Hart conceding more than five – a situation that may necessitate a change in tactics later in the race.
The bright spot for the British team came via Geraint Thomas, who looked impressive on the final climb, steering clear of trouble to finish eight seconds behind Alaphilippe.
‘It’s a really special victory’
While the chaos was still unfolding behind him, Alaphilippe distanced his rivals with a devastating solo attack 2.3km from the line.
He had been expected to face stiff competition from Mathieu van der Poel and both Roglic and Tadej Pogacar mounted unsuccessful chases to reel the Frenchman in.
Neither came close to catching him and it ensured France’s first opening stage winner since Christophe Moreau in Dunkirk in 2001 and a sixth stage win at the Tour for the 29-year-old who will now wear the yellow jersey for a third consecutive year.
“It’s a really special victory for me. I’m changing jerseys but there are worse jerseys to wear,” Alaphilippe said.
“It’s a scenario I imagined and I really wanted to do it – it’s really super.
“My team did a great job and controlled it all day. At the end I was caught in a crash but we got back and I really had to make the last climb. I had to get rid of the sprinters. It wasn’t easy but I gave my best and that was it.”
Stage one results
1. Julian Alaphilippe (Fra/Deceuninck-Quick-Step) 4hrs 39mins 05secs
2. Michael Matthews (Aus/Team BikeExchange +8secs
3. Primoz Roglic (Slo/Jumbo-Visma) Same time
4. Jack Haig (Aus/Bahrain-Victorious)
5. Wilco Kelderman (Ned/Bora-Hansgrohe)
6. Tadej Pogacar (Slo/UAE-Team Emirates)
7. David Gaudu (Fra/Groupama-FDJ)
8. Sergio Higuita (Col/EF Education-Nippo)
9. Bauke Mollema (Ned/Trek-Segafredo)
10. Geraint Thomas (GB/Ineos Grenadiers)
General classification after stage one
1. Julian Alaphilippe (Fra/Deceuninck-Quick-Step) 4hrs 38mins 55secs
2. Michael Matthews (Aus/Team BikeExchange +12secs
3. Primoz Roglic (Slo/Jumbo-Visma) +14secs
4. Jack Haig (Aus/Bahrain-Victorious) +18secs
5. Wilco Kelderman (Ned/Bora-Hansgrohe) Same time
6. Tadej Pogacar (Slo/UAE-Team Emirates)
7. David Gaudu (Fra/Groupama-FDJ)
8. Sergio Higuita (Col/EF Education-Nippo)
9. Bauke Mollema (Ned/Trek-Segafredo)
10. Geraint Thomas (GB/Ineos Grenadiers)
