Arnaud Démare (FDJ) won a hectic sprint into Vittel to take his first win at the Tour de France, but his success was overshadowed by a high-speed crash in the finishing straight that left Mark Cavendish (Dimension Data) on the ground and saw Peter Sagan (Bora-Hansgrohe) disqualified from the race for sparking the crash.

Démare was ahead of the carnage in a select group of sprinters that had avoided a crash with a kilometre to go that involved race leader Geraint Thomas (Team Sky) and several others. He came past French rival Nacer Bouhanni (Cofidis) along the barriers and then cut to the centre of the road to beat Alexander Kristoff (Katusha-Alpecin) at the line.

Behind him riders fought for his wheel. Cavendish was there but Sagan moved to the barriers to follow the Démare, not seeing or not caring that Cavendish was coming up fast. It was a risky move by the Manxman to try to follow Démare but his only other option was to brake and lose any chance in the sprint. He chose to take a risk but as the sprinters rippled towards the barriers, his way through was closed. Cavendish tried to stay upwards but lost his balance and hit the barriers at speed.

Sagan made matters worse by sticking out his elbow as he tried to stay up. Behind them, John Degenkolb (Trek-Segafredo) and Ben Swift (UAE TeamEmirates) had nowhere to go and flew over the top of Cavendish, who was already lying on the ground.

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Cavendish got up but had suffered multiple injuries, including to the shoulder he injured in the 2014 Tour de France sprint crash in Harrogate, and a cut to a finger.

"I will definitely need stitches in this finger, it's bleeding a lot. With the shoulder, it might be something to do with a previous injury; it's sat backwards so I'm not sure if I've done something to the ligament. I'm not a doctor but from the feelings I'm not optimistic," Cavendish said of his injuries before questioning Sagan's move in the sprint.

"I get on with Peter well but I don't get it... If he came across, it's one thing, but the elbow... I'm not a fan of him putting his elbow in like that. A crash is a crash, but I'd just like to know about the elbow."

Sagan went to the Dimension Data bus to apologise but he did not get a warm welcome.

"Mark was coming pretty fast from the back," Sagan said. "I didn't have time to react and go left and he just came to me and after into the fence."

The UCI commissaires didn't agree and after seeing the replay of the sprint several times, they first relegated Sagan to 115th place – the last place in the group that finished on the same time, and gave him a 30-second penalty. Two hours after the finish of the stage the UCI commissaires appeared in the Tour de France pressroom to confirm that Sagan had been disqualified altogether.

Late drama

It had been a very quiet stage, marked only by a courageous long solo breakaway by Guillaume van Keirsbulck (Wanty-Groupe Gobert), but it ended with the biggest rider in the sport being thrown out of the race.

While much of the post-stage attention was on the crash and Sagan's disqualification, Démare and his FDJ team celebrated their success. It was Démare's first Tour stage win, and the first victory by a Frenchman in a bunch sprint since Jimmy Casper won in Strasbourg in 2006.

"This win is extraordinary. It's marvellous. I've dreamed about winning a stage at the Tour de France since turning professional," Démare said.

"It was tough in my first Tour in 2014 but today I had really strong team, even with a guy like Mikel Delage doing his bit despite being injured. He helped me stay up front, then Cimolai and Jacopo Guarnieri lead me out. I thought I was going to lose it in the final metres but I had good legs and I got it."

In the final official results, Kristoff was confirmed as second, with Andre Greipel (Lotto Soudal) third and Nacer Bouhanni (Cofidis) fourth.

The rest of the peloton finished in small groups due to the two crashes and testing finish.

Overall leader Geraint Thomas (Sky) crossed the line several minutes after Démare but thanks to the rules for crashes inside the final three kilometres, he was given the same time as the Frenchman and so kept the yellow jersey

"Luckily I'm okay. I managed to scrub off a lot of speed but there was nowhere to go really. That's the way it goes. I'm used to crashing so it's fine! I'm all okay," he said, confirming that teammate and team leader Chris Froome had avoided the crash.

"Froomey is fine and he managed to miss it all. It was a good day in the saddle for him. It wasn't nice to ride past Cav still on the floor. These sprints are just always hectic."

Thomas will wear the leader's yellow jersey during Wednesday's 160km fifth stage to La Planche des Belles Filles. It is the first mountain finish of this year's race and should see the first battle amongst the overall contenders.

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