A dropped chain was the latest misfortune to befall Mark Cavendish as Dylan Groenewegen doubled up at the Tour de France with his second win in as many days.

While the Dutchman followed up Friday’s success in Chartres with a Bastille Day victory in Amiens on stage eight, Cavendish could enjoy a respite from questions over his form as there was little he could have done differently this time.

The Manxman, looking to turn around a frustrating start to the Tour, was on the wheel of Peter Sagan as the peloton rounded a left-hander on to the finishing straight with 600 metres to go.

But when Sagan launched – too early as it turned out – there was no response from Cavendish as his equipment let him down.

“What can you do?” he said. “The chain comes off with 250 metres to go. At least it stops me having to think of excuses. I was in the perfect position. I was pretty happy.

“Coming around that corner with three kilometres to go, we knew it was pretty sketchy. I lost my leadout men but I was alright. I followed Sagan, but following him is pretty sketchy – he bashes everyone else out the way so you do get a clear run following him.”

After catching Sagan, Quick-Step Floors’ Fernando Gaviria and Lotto-Soudal’s Andre Greipel clashed and were both relegated, but though the German reacted angrily on Twitter his punishment was for a seperate incident involving Team Sunweb’s Nikias Arndt.

The decision moved Sagan up to second, with Trek-Segafredo’s John Degenkolb third. Cavendish was elevated to eighth.

BMC’s Greg Van Avermaet retained the yellow jersey and snatched a second in the bonus sprint to extend his lead over Team Sky’s Geraint Thomas to seven seconds.

Most of the general classification contenders crossed the line in the main bunch but it was a costly and bruising day for UAE Team Emirates’ Dan Martin, who was caught in a crash with 17km to go.

The Irishman, winner of stage six on the Mur-de-Bretagne, rode home with blood pouring from his elbow. After finishing 76 seconds behind the lead group he was seen virtually crawling on to his team bus in pain.

An x-ray found nothing was broken, but Sunday’s stage nine over the cobbles to Roubaix promises to be punishing.

“I’ve felt better obviously, but it’s not as bad as (it could be),” he said. “Nothing’s broken. I’m going to try and ride tomorrow, to get over the cobblestones, but it’s going to be sore.

“You know it’s bad when, just then to do the scan they took the bandages off and the doctor went, ‘Ooh’. It could have been a lot worse and it was just wrong place, wrong time…

“At the end of the day I won a stage in the Tour this year. I said whatever happens from now on is a bonus. This isn’t the bonus I was thinking of but it happens.”

Those cobblestones lie on Sunday’s mini-version of Paris-Roubaix, a race popularly known as ‘the Hell of the North’. A total of 21.7km of cobbles await on the 156.5km stage north from Arras.

Adam Yates’ Mitchelton-Scott team-mate Mathew Hayman, who won Paris-Roubaix in 2016, said he fears at least one general classification contender could see his race ended on roads known for causing crashes and mechanicals.

“I’m not 100 per cent sure we should be putting cobbled stages in the Tour de France,” he said. “I’m a Classics rider and a specialist and I love the cobbles. But I see the effort these guys put in, the months of preparation and wonder if maybe eliminating some of them just through bad luck is right.”

Four-time winner Chris Froome saw his 2014 Tour ended on a similar cobbled stage – though he never even made it to the first sector that year – and the Team Sky rider expects a major shake-up of the general classification.

“It could go either way tomorrow,” he said. “A lot of it will be about luck, staying out of trouble, not having a puncture or a mechanical at the wrong time or caught in a crash.

“There are going to be losses on GC and it just depends what side of that you are on – we hope to be on the right side.”