The 100th anniversary edition of the 24 Hours of Le Mans is underway in challenging, wet-dry conditions.

At exactly 15:00 CET (00:00 AEST), the flag dropped on the most anticipated race of the year, Antonio Fuoco leading the way around the famous 8.4-mile Circuit de la Sarthe after the Italian took pole position in Ferrari’s #50 499P in a time of 3:22.982s.

The Safety Car for the traditional rolling start had led the 62-car field away at 14:51, completing a single lap before they were unleashed.

Drops of rain began to fall in the humid conditions, with sections of the track treacherously damp to keep the drivers on their toes. Half the circuit looked outright wet, half bone dry.

Storms and heavy rain are expected later in the afternoon and into the evening in north-west France.

Fuoco led on to a damp and tricky Mulsanne straight, but Sebastien Buemi in the #8 Toyota was on the move from third on the grid, the Swiss taking the lead on the run to Indianapolis.

The Toyota led at the end of Lap 1 from Fuoco, the #7 Toyota of Mike Conway, the #51 Ferrari of James Calado and the #75 Porsche of Felipe Nasr.

But there was disaster for Briton Jack Aitken in the Action Express Cadillac, which snapped left on the exit of the damp first chicane on the Mulsanne and slapped hard into the barrier.

The Caddy had heavy front-end damage and broken suspension on the left wheel, while a Safety Car period was called for barrier repairs.

Paul Loup Chatin led the LMP2 class at the end of Lap 1 for IDEC Sport having started from the class pole.

Likewise, the pace-setting Corvette of Nicky Catsburg headed the GTE Am field.

Meanwhile, the ‘Garage 56’ NASCAR Chevrolet Camaro started by Mike Rockenfeller continued its incongruous Le Mans adventure, completing the first lap in 36th overall, ahead of the GTE runners.

Toyota remains the favourite for victory – despite a controversy over a late and unexpected change to the Balance of Performance.

The big question is whether Ferrari can take the fight to the Japanese cars, having locked out the front row of the grid, and whether Porsche and Cadillac have the speed to mount their own challenges.

The weather is likely to be a significant factor in shaping fates. Negotiating traffic without incident will also be key, more than ever with the higher count of top-class Hypercars this year.