Childhood friends are set to run a gruelling six day marathon, in the scorching heat of the Sahara.

Andy Prickett and Kieren Unwin, both 29, are taking on the infamous Marathon des Sables.

The 156 mile ‘ultramarathon’ is based in southern Morocco, where temperatures regularly soar above 50 degrees.

It is widely regarded as the toughest footrace on earth, covering a distance equal to five-and-a-half marathons.

The pair, who will scale enormous dunes and face a battering from sandstorms on their arduous journey, have been running 80 miles a week in preparation.

They will also be saddled with 10kg backpacks, containing food, cooking equipment, medical supplies and sleeping bags.

Mr Prickett, from Earlsfield, said: "It’s going to be pretty difficult. The temperatures could be as high as 52 degrees, and sand is really tricky to run on.

"We also have to be entirely self-sufficient, the only thing they will give us is water."

They hope to raise £50,000 for the Atkinson Morley Neurosciences Research Foundation which will be used to fund work on the Atkinson Morley Wing at St George’s Hospital in Tooting after Mr Unwin was successfully treated there for a brain injury.

When he was two-years-old he fell from a 15ft balcony, cracking his head on the tile floor below.

He spent days in a coma.

Mr Unwin, from Clapham, said: "My family are really grateful to all the staff, and one of my friends was successfully treated there recently.

"It is such an important part of the hospital that has saved literally hundreds of lives.

"They saved my life so it is a cause very close to my own heart."

Friends since they were five-years-old, they have been doing Bikram Yoga three or four times a week in preparation for the heat.

The practice involves doing 26 postures in 40 degrees heat, with each session lasting 90 minutes.

The two fundraisers will begin the marathon on April 6 and finish on the 11th, with only one day of rest four days in.

They started fundraising in August last year, and have held a carol concert, a charity golf day, and ran half marathons to raise the cash.

So far they have collected nearly £37,000.

Mr Prickett, a property developer, said: "We are really grateful to everyone who has sponsored us and helped out so far.

"There is not long to go now until the race, and our target is definitely in sight.

"It’s going to be tough, but raising the money will definitely make it all worth it."

To make a donation visit: http://uk.virginmoneygiving.com/mds2014