The 107th edition of the one-day race had been due to be contested over 291 kilometres but a landslide on part of the route caused organisers to arrange for a detour, adding a further four kilometres.

Typically the main action at the race was saved for the final 25km with Italy’s Giovanni Visconti, Daniel Oss, Matteo Montaguti, Fabio Sabatini and Britain’s Ian Stannard launching a move on the Cipressa climb.

The break was quickly hauled back ahead of the Poggio at six kilometres to the finish, where Poland’s Michał Kwiatkowski and Italy’s Vincenzo Nibali attempted an escape of their own.

The race was decided, however, via a bunch sprint.

Several of the main contenders saw their hopes dashed by misfortune.

Colombia’s rising star Fernando Gaviria, who defended his world omnium title on the track in London earlier this month, crashed after a touch of wheels.

His accident halted the sprint of Slovakia’s Peter Sagan, the reigning world champion, and France’s Nacer Bouhanni suffered a mechanical problem in the final kilometre to halt his challenge.

Demare took full advantage of the chaotic finish to claim victory in the time of 6 hours 54min 45sec.

It made the FDJ rider the first Frenchman to win Milan-San Remo since Laurent Jalabert in 1995.

"This is incredible, there are days like this one in which everything works despite the occasional hiccup, like crashing at the bottom of the Cipressa,” Demare, a 24-year-old from Beauvais, said. 

“I made it across at the bottom of the Poggio and the entire way I felt fantastic.

“I became the under-23 world champion in similar conditions after crashing, I'm delighted to win Milano-San Remo.

“This is a big one and has been running for over a century, it's extraordinary, I'm extremely happy."

Britain’s Ben Swift bettered his third place from the 2014 edition of the race to finish runner-up, on the same time as the winner.

Belgium’s Jürgen Roelandts was also awarded the same time to complete the podium places.