Following graduation Stephenson joined the British Arctic Air Route Expedition to Greenland as chief surveyor. In often difficult polar conditions the expedition surveyed a strategic area of Greenland valuable to the Great Circle air route between the British Isles and North America, work for which Stephenson was awarded the Polar Medal. Despite his inexperience as a climber he held the altitude record of Mont Forel at 10,950 ft with his companion Lawrence Wager for many years, even though they were not able to reach the 11,099 ft high summit owing to the ice dome at the top.