Through the 1920s, the interest of the British authorities had grown in the unmapped and uninhabited territories of the Shaksgam Valley because it provided access to the Aghil Pass linking China to Ladakh, India. Mason began a survey using a photo-theodolite and stereographic techniques, laboriously collecting great quantities of data. His results, plotted in Switzerland using what, at the time, was the world's most advanced Stereoplotter, were acclaimed as brilliantly successful and won him the award of the 1927 Royal Geographical Society's Founder's Gold Medal. While Mason had failed to fully descend the Shaksgam Valley he had been able to explore the Aghil range in the Karakoram fault system and discovered the valley of the Zug Shaksgam.