It’s easy to think that an expedition is all about using physical strength to overcome obstacles. And whilst it’s true to say that power, agility and stamina play a big part in the overall success of any expedition, the game is won or lost in the mind.

I’ve been fortunate to spend extended periods of time with Martin on expeditions to the Himalaya, the Pamirs, and the Arctic. And I was, with Simon Harris-Ward, Pen’s UK Base Camp Manager for his 2003/04 South Pole expedition. They are two of the psychologically toughest people I know, but even they must be feeling it after three brutal weeks on the ice.

The coldest I’ve personally encountered is -100 degrees Fahrenheit (-73 degrees Celsius) on Alaska’s Mount McKinley in 1992. That was a combination of -40 degrees ambient (top Trivial Pursuit info: this temperature is the same in Celsius and Fahrenheit) plus 100 mph (160 kph) windspeeds. When our tents broke, we dug snowcaves and lived like moles for a week until we thought the worst was over. (We were wrong, but that’s another story).

In these kind of temperatures, your mental field of vision can become very narrow. Constantly running through a mental checklist of how your extremities are doing, attempting to keep the creeping cold at bay, and trying to find little ways to minimise the discomfort soak up a lot of your time and energy.

It’s easy in these temperatures to become frustrated with yourself, your team-mates and your kit. The fact that it took Martin a week to find a sewing needle burrowed in his bum gives you some idea of how weary they must all be feeling right now. That they are remaining on excellent terms with each another speaks volumes about their personalities.

Any seasoned expeditioner will tell you that pretty much anything is bearable, providing that one has the ability to enjoy a warm and dry night's sleep. However, for various reasons the team chose not to take vapour barrier liners for their sleeping bags, and now with a sudden warming (up to a sultry -24 from a nippy -40 degrees Celsius) their frozen sleeping bags are just starting to feel like sorbets.

Try spending tonight sleeping on the kitchen floor with a drawing pin stuck in your backside, and a duvet cover full of ice cubes, and you’ll start to gain an appreciation of the miserable living conditions they are enduring. Martin recently wrote that he can think of 20 million things he would rather be doing right now, and I believe him.

Which brings me on to my final point. An expedition of this length is a marathon, not a sprint. (Actually, it’s more like 35 to 40 marathons). They’ve completed over 20 days, with around 60 still to go. The only way to get through such an extended journey is to treat it like you’re eating an elephant, namely one bite at a time.

If this description of the mind games on an expedition leaves you with the distinct impression that some people tick off the days between each expedition, desperate to leave behind all the trappings of civilisation, only to count away the hours whilst on an expedition, longing to return home, you’d be only partly right. When the going gets tough, the challenge is to be comfortable with yourself, in whatever situation you find yourself in, and to recognise that a storm (be it real or metaphorical) ultimately blows itself out. The trick is to hang on in there for the sunrise.