Welshman Paul Fosh takes on Yukon Arctic Ultra marathon

Competitors must drag all their supplies across 430 miles of Arctic conditions

It is billed as the world's coldest and toughest ultra-marathon, previously only undertaken with huskies.

The Yukon Arctic Ultra is a gruelling 430-mile trek through endless snow and ice, where temperatures plummet to as low as -40C.

It begins in northern Canada and ends close to the Alaskan border, though few actually reach the finish line.

And Welsh auctioneer Paul Fosh, 52, is joining a select group of British athletes to complete the mammoth task.

Competitors walk across the Yukon Territory in northern Canada

Mr Fosh, from Monmouth, will run, walk and crawl over some of the world's wildest and coldest terrain.

In addition he must carry food, water, sleeping gear and emergency supplies on a sled - a 'pulk' - the entire distance of the epic race

Most of the time he will have to contend with temperatures ranging between -25C and -40C.

Conditions are so brutal that last year only one of the 23 competitors who began the full distance race made it to the finish line.

"I love the challenge, both physical and mental but know that probably less than a quarter of those entering the race will complete it," Mr Fosh said.

"Over time, you become thrilled to be part of the small percentage that have entered and completed the race.

"I have invested a lot of time, effort and money to get myself out there and I want to do myself proud. I don't ever want to fail at anything I do."

Paul Fosh has previously competed similar challenges - but not on this scale

Competitors have 13 days to complete the challenge and Paul aims to average more than 40 miles a day.

The route crosses frozen rivers and lakes, while markers are regularly covered with fresh snow.

Frostbite is a constant peril hanging over every racer. Last year, an experienced ultra-runner from Italy lost part of both legs and an arm to the condition.

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Between the checkpoints, Mr Fosh is on his own and competitors often complain of hallucinations amid the relentless wilderness.

"A lot of people underestimate the mental challenge," he said.

"Walking in the daylight is much easier psychologically because you've got such fantastic scenery to look at. But when you're walking at night, you could be anywhere. You've just got your head torch beam to follow.

"There are those of us that almost enjoy the pain, but if it was too easy there would be no pleasure at the end."

Mr Fosh owns an auction house in Newport

The kit on the sled will contain a sleeping system, consisting of a sleeping bag, light tent, stove, freeze-dried meals, first aid kit, emergency equipment - and lots of layers of clothing.

Mr Fosh aims to raise money for a charity aiming to end homelessness in Wales.

He trained for the event by dragging tyres around the hills and countryside near his home in Monmouthshire for up to 12 hours at a time.

He said: "I know my level of fitness is right to achieve this goal, I have been doing a lot of training for this one as it is the most demanding races I've ever done.

"Someone once told me to train hard and play easy. Admittedly, that was in the context of rugby, but I think it can apply to this too."