I think that's all from me today. I'm going to try and make sense of all that in the race report, which is already under way.

There will be more reaction in there and as soon as we hear anything about Mark Cavendish's condition we will, of course, report on it.

Don't forget BeSpoke from the Tour de France with the BBC Radio 5 live team. They are live tonight on Facebook and there will also be a podcast to follow and they will discuss today's incidents and update with any info as they get it.

Tomorrow's stage begins at the slightly later time of 12:00 BST and I'll be back then for that. It promises to be a huge day for the general classification riders with the first mountain-top finish of this year's race, where Chris Froome won his first Tour stage in 2012.

Thanks for your company today. Let's go again tomorrow.

Image source, Tour de France

Race leader Geraint Thomas has also been talking about his spill and he is better off.

"I'm alright," he said. "It was just a crash in front of me and I had nowhere to go.

"Luckily i took off most of the speed. I think Chris Froome managed to get round it and he's OK."

He says Peter Sagan offered an apology.

He added: Injury-wise I'm going to get it checked out. I need stitches in a finger. And the shoulder. It's something to do with the shoulder that I hurt in Harrogate (on stage one of the 2014 Tour de France). I'm not a doctor but I'm not optimistic.

"I was following Demare and then Sagan came over. I get on well with Peter but I'm not a fan of him putting his elbow in. A crash is a crash, i'd just like to know about the elbow."

Kate Fairhurst‏, external: Astonished at what I've just seen on @LeTour, external - @PeterSagan, external *seemed to* push @MarkCavendish, external into the barriers. Straight DQ IMHO.

Sam Levey, external: Can't work out if Sagan is off balance due to Greipel(?) on outside or whether he's defending the inside. Awful for Sir Cav.

#bbccycling

No big surprises there.

His Dimension Data team director Roger Hammond is clearly not happy and says "if I was Sagan I would apologise".

He adds: "He's being looked at by the team doctor. A crash that close to the finish is never good and he's going to radiology.

"He has some cuts and his hand is injured but it's too early to say what they are."

We are still waiting to hear from either Mark Cavendish (unlikely, I would imagine), or Peter Sagan (possible - he's already talked about something to do with Andre Greipel, although that was short and sweet and had a word I can't repeat on here).

Sagan actually ended up second on the stage and he picked up six bonus seconds to move up to second overall, with Chris Froome dropping to third.

1. Geraint Thomas (GB/Team Sky) 14hrs 54mins 25secs

2. Peter Sagan (Svk/BORA) +7secs

3. Chris Froome (GB/Team Sky) +12secs

4. Michael Matthews (Aus/Sunweb) Same time

5. Edvald Boasson Hagen (Nor/Dimension Data) +16secs

6. Pierre Latour (Fra/AG2R) +25secs

7. Philippe Gilbert (Bel/Quick-Step) +30secs

8. Michal Kwiatkowski (Pol/Team Sky) +32secs

9. Tim Wellens (Bel/Lotto) Same time

10. Arnaud Demare (Fra/FDJ) +33secs

1. Arnaud Demare (Fra/FDJ) 4hrs 53mins 54secs

2. Peter Sagan (Svk/BORA) Same time

3. Alexander Kristoff (Nor/Katusha)

4. Andre Greipel (Ger/Lotto)

5. Nacer Bouhanni (Fra/Cofidis)

6. Adrien Petit (Fra/Direct Energie)

7. Juergen Roelandts (Bel/Lotto)

8. Michael Matthews (Aus/Sunweb)

9. Manuele Mori (Ita/UAE Team Emirates)

10. Tiesj Benoot (Bel/Lotto)

Sagan and Cavendish are having a bit of a chinwag. Cav puts his arm round the Slovakian. No idea what was said there.

From the rear view, it looks like Sagan flicked out an elbow. From the head-on shot, it looks more like Sagan was trying to keep his balance.

Cav was on the wheel of Demare and as the two went down the right of the road, Sagan came across and there was nowhere to go but into the barriers.

Amid all that, Geraint Thomas crossed the line a couple of minutes or so after stage winner Arnaud Demare. But he will retain the yellow jersey because on sprint stages if you crash in the final 3km, you are awarded the same time as the group you were with and in G's case, that was Demare.

That's why the GC guys have to get involved in the sprints.

Matt Taggart‏, external: Surely that was an elbow from Sagan? Are we going to see a DQ?

I don't know Matt. It will be a big call from the race officials. It will be interesting to get Sagan's take on it.

Image source, Reuters

Cavendish has crossed the finish line. Rob Hayles says that he is not holding his handlebars with his right hand. It could be a broken collarbone.

I want to see another repeat of that Sagan flick. There was definitely movement and the race officials may not take too kindly to that. I can't imagine Cav will be too happy either.

It looks like Cav was trying to sneak up the inside of Peter Sagan and the world champion looked to flick out an elbow and knock Cav into the barriers.

We may not have heard the last of this.

After all that Arnaud Demare becomes the first Frenchman in more than a decade to win a bunch sprint finish.

But it's all about Cavendish for me. The medics have reached him and are tending to him. Geraint Thomas pedals by, looks over and realises that it's his mate on the deck.

This could be the end of the Tour for Cav.

Arnaud Demare wins stage four

Image source, Reuters

Mark Cavendish is still on the deck. It could be his collarbone again. Geraint Thomas is back up and pedalling.

More on the crash later. G looked OK.

Here's the finish. Andre Greipel is in pole position but Mark Cavendish goes down. He's pushed into the barriers hard.

Image source, AFP

Edvald Boasson Hagen has to keep going for another kilo here. Mark Renshaw is in front of Cav Big crash. Geraint Thomas goes down.

Geraint Thomas and Chris Froome are still in the first 20 on the road. Dimension Data take over the pace-setting. They are doing everything they can for Cav.

Marcel Kittel is coming up, he has two team-mates in front of him but is about 40 riders back. 2km to go

Here we come into Vittel. It doesn't look like a particularly big place.

Poor old GvK has gone out the back of the peloton. He is pedalling squares.

Up at the front Katusha are pushing on, looking to set up Kristoff.