Twenty-nine-year-old Ed Fernon conquered the gruelling Mongolian Derby, crossing the finish line with South African Barry Armitage in equal first after a nail-biting race to the finish.

The 2017 race saw 12 men and 24 women from nine countries riding 1,000 kilometres across Mongolia on semi-wild horses.

Mostly riding full tilt, they charge through the rugged terrain of the Mongolian Steppes, fording rivers, deserts and wide open plains on a course that is designed to recreate Genghis Khan's ancient postal system.

It puts to the test the competitor's survival skills, horsemanship and sheer endurance.

Competitors change horses every 40 kilometres and camp out under the stars or stay with local herders.

Horses will often injure the participants if badly handled, and riders are also given penalties if they overwork the tough Mongolian ponies.

Although city born, he spent time on a family farm near Wagga Wagga in NSW where he first threw his leg over a horse.

His love of riding inspired him to take up the modern pentathlon, mastering the five disciplines of swimming, fencing, running, shooting and show jumping.

He started the sport as a 20-year-old and four years later represented Australia in the 2012 London Olympics.

Needing a new challenge post-Olympics, Fernon did a charity ride across the snowy mountains.

The ride retraced the 1,100 kilometre journey of Archer, the legendary horse that walked from NSW to Melbourne before winning the inaugural Melbourne Cup in 1861.

"Following the Legend of Archer" raised over $50,000 for The Black Dog Institute, offering support for people suffering from depression and bipolar disorder.

Fernon crossed the finish line of the Mongolian Derby exhausted and exhilarated.

"Regardless of winning, what I came here for was to challenge myself, give it my all, and I've done that. I'll sleep well tonight," he said.

Just to complete the hardest horse race in the world is an achievement few can boast.