Imagine trekking 600 miles on treacherous terrain carrying 15 kilos with minimal sleep, all while racing against the clock.

Sutton brother and sister duo James, 21, and Natalie Gardner, 29, will be doing exactly that when they compete in the Patagonian Expedition Race in Chile next month, all while raising money for charity.

The exhibition, dubbed ‘world’s toughest adventure race’, sees competitors trek, climb, kayak, ride, and navigate through unchartered land over ten days – often covering hundreds of kilometres without seeing another person.

Their four-person team, the Green Sentinels, have been training for 18 months to prepare for the race.

Miss Gardner said: “The 600 miles is mostly going to be on foot so we have been trying out different packs doing long distance, weighted, fast walking to build muscle memory and get used to the aches and pains we will be feeling out there.

“The main thing about the race is navigation, James has done a navigation course and I have done mountaineering navigation courses myself.

“A lot of this is about skills and mental fitness, they say your mind will give out before your body will.

“While it is going to be difficult physically, it’s finding the mental strength to just carry on going when you are in pain and you’re starving and freezing.

“All of the race is in unchartered territory, if we take a route through the mountains we are going to be the first people that have done that route.

“The scenery is going to be incredible and we are hoping that when our morale is low and we are trying keep each other going that we can stop for a minute and look around to appreciate where we are.

“We are just going to have to give this everything we have got, unless we break a bone or pass out or fall down a crevasse we are just going to have to keep each other going.”

The race starts on February 13 and runs until February 26.

The team have to carry all of their supplies, including sleeping bags, navigation tools, climbing gear, clothes, harnesses and food.

They will need to consume 5,000 calories per day eating every half hour to survive the race.

All money raised will go to the Royal Marsden Cancer Charity, Shelterbox disaster relief and Help for Heroes.

To donate visit virginmoneygiving.com/greensentinels