Pen Hadow's personal trainer Jon Stratford was in the Royal Marines for 14 years and devised a series of fiendishly tough workouts to prepare the Catlin team for their expedition.

He trained them on Dartmoor because the undulating terrain is similar to the Arctic. Minus the snow and ice, of course.

Now watch our third Catlin Arctic Survey episode, which focuses on the innovative kit the Catlin team are carrying with them on their trip.