Good morning and welcome to live coverage of the 115th edition of Paris-Roubaix: the Hell of the North, the Queen of the Classics, the brutal dusty/muddy one with the cobbles where everyone falls off or collides with spectators... call it what you want, this is the big one, and the third monument of the season.

Tony Martin rides clear of the pack as they complete sector 26, the fourth sector of cobbles. He has a small gap over the pack. The German showed how well he can ride the cobbles with a victory on these roads in the Tour de France in 2015. He could prove an invaluable foil for Alexander Kristoff today.

The Sky rider who went down in that Naesen crash was Lukas Wisniowski, the Polish youngster making his debut in the race.

CRASH: There's a touch of wheels towards the back of the peloton which sees a cluster of riders go down just as a second peloton were riding back on. The cobbles have already caused carnage with riders and groups stretched out all over the roads.

Some better images of that huge crash earlier...

Luke Durbridge of Orica-Scott - one of the main lieutenants for defending champion Mat Hayman - is riding back onto the peloton after some issues. The leaders are now onto 26 / 3km / *** / Viesley-Biastre.

Terrible luck for Oliver Naesen, the young Frenchman who was riding so well last Sunday until that crash which saw him, Sagan and van Avermaet all come down on the Kwaremont. Naesen is back in the wars today after that crash on the opening sector and he needs attention from the Ag2R car - for a mechanical issue we're hearing.

The two leaders have finished the third sector and have a gap of 55 seconds on the pack, which is being led by Germany's Andre Greipel - until Katusha swing through. Peter Sagan is very prominant.

Here's that original crash, which happened just as Eurosport were running an interview with Luke Rowe of Team Sky. It looked like someone clipped something on the verge and it caused a bit of chaos, with one rider going right over the bars and at least one more ending up in a muddy ditch. Not sure who the Sky rider was but it was Lampaert for Quick-Step and Oliver Naesen for Ag2R-La Mondiale.

Another crash: this time on a tight right-hand bend before the third sector. Tony Gallopin of Lotto Soudal is involved, but not critically injured or anything.

CRASH: Half a dozen riders come down near the front of the pack - including bodies from Sky, Quick-Step and Ag2R-La Mondiale. That was a nasty one.

The leaders are onto the next sector: 27 | 3 700 m | **** | Quievy - Saint Python | 151.0 km to go. Martinez has been dropped by the other two escapees.

Katusha, Team Sky and Quick-Step all on the front - as is the world champion Peter Sagan, who has made a big effort to move onto the front. He crashed badly last week in the Tour of Flanders when clipping the barriers on the Oude-Kwaremont, and since then he's had a rather fetching haircut...

We're onto the second section of cobbles: 28 | 1 800 m | *** | Viesly - Quievy | 153.5 km to go. The gap is up to 1:05 for the leaders.

It's already a real elimination race as the peloton stretches out considerably. The lead is still just under 50 seconds for the three leaders, who have two riders in pursuit: Kenneth Vanbilsen (Cofidis) and ?.

The three leaders have survived the first sector. Meanwhile, Tony Martin - formerly of Quick-Step and now of Katusha - is on the front of the dust-covered peloton.

Team Sky and Quick-Step lead the pack onto the first cobbled sector at Troisvilles. Both teams have high hopes today: Sky have two cards to play in Ian Stannard (third last year) and Luke Rowe, perhaps even Gianni Moscon; Quick-Step have that man Tom Boonen, plus a raft of Plan Bs in Niki Terpstra, Zdenek Stybar, Matteo Trentin and Yves Lampaert.

Here we go... it's the cobbles! Let the Hell of the North commence... the gap is 47 seconds for the three leaders.

The gap is up to 40 seconds now for the three leaders: Yannick Martinez (Delko Marseilles Provence KTM) was joined by Jelle Wallays (Lotto Soudal) and Mickaël Delage (FDJ). There are a few others trying to bridge over.

The first sector is Troisvilles-Inchy / 2.2km / *** / 160km to go. And we have a photo sent through by a follower on Twitter... here's what the riders have to expect.

Just one rider out in front now - from the French wildcard team Delko Marseilles Provence KTM. It's Yannick Martinez on a crazy bid to lead the race onto the first stretch of cobbles. He probably wished someone came with him... and someone has now done just that: Lotto Soudal and FDJ send riders clear of the pack.

The Katusha riders is Marco Haller and he's with Wang Meiyin (Bahrain-Merida) - or at least, he was: they've been reeled in with 10km until that first cobbled section.