The Ultra-Trail du Mont Blanc

Into the unknown: Blake, Duncan and Cal (left to right) depart their hotel for the start of the race Photograph: Personal

Mass appeal: It’s standing room only as the 2,600 runners converge on the centre of Chamonix for the countdown Photograph: Personal

On the line: The start, with snow-capped Alps beyond Photograph: Personal

Under orders: Apprehension and excitement as the runners prepare for the starting gun Photograph: P Tournaire/UTMB

They're off: The first few paces of a race that will last up to 46 hours Photograph: P.Tournaire/UTMB

Early lead: A lone runner, with the dramatic peaks of the Mont-Blanc Massif beyond Photograph: Newspower Canon/UTMB

Valley of death: Runners navigate some brutal terrain 50 miles in Photograph: Jean Pierre Clatot/AFP

At one with nature: The course takes runners into areas inhospitable to all but the hardiest animals Photograph: P. Tournaire/UTMB

Above the clouds: Nearing one of the many summits Photograph: P. Tournaire/UTMB

Down but not out: Duncan concentrates on a tricky descent Photograph: Vincent Guerrier/flash-sport.com

Sloping off: Cal (middle) pauses during a vicious descent Photograph: Personal

Sting in the tail: Cal (left) and Blake pause for breath midway up the Col des Montets Photograph: Personal

Painfully beautiful: A runner summits the final peak with Chamonix visible in the valley below Photograph: P Tournaire/UTMB

Final Burst: Duncan (left) and Blake savour their moment of glory Photograph: Vincent Guerrier/flash-sport.com

Pround moment: Blake (left) and Duncan at the finish Photograph: Personal