[6] He was elected fellow of the Royal Society of Edinburgh in 1925 and, succeeding Sir Lewis Leigh Fermor, he became the Survey's director in 1936 until stepping down from that post in 1939.

In letters home to his wife Ruth he wrote that Heron was a "solid treasure", was "cheerful and good-natured", and that although he was good at dealing with the porters he was no climber.

[14] Starting from the expedition's base at Tingri on 25 June, Heron set off south west towards the Kyetrak Glacier with Oliver Wheeler.

Howard-Bury joined them later and while Wheeler surveyed on his own, they explored the area of the Nangpa La where Heron discovered marine fossils in the limestone at heights never thought possible.

[15][16][note 1] By 4 July they had moved to see Mallory and Guy Bullock in the Rongbuk valley and then they headed on north and then east to find a suitable base from which to explore the eastern approaches to Everest.

He returned to Kharta on 19 August after exploring, in very bad weather, a broad east-west region as far north as the Yarlung Tsangpo River.

Nearer to the mountains the shale was underlain by limestone (possibly Triassic or Jurassic) metamorphosed into crystalline form and into calcareous gneiss.

It included the basin of the Arun River, the region north and east of Everest, and in the west the headwaters of the Bhote Koshi flowing into Nepal.

The Arun Gorge is 5,000 feet (1,500 m) deep as it cuts completely through the Himalayan ridge and for the origin of its upper part Heron was "unable to give an explanation".

[29][note 2] While the expedition was underway, on 28 September 1921, Charles Bell, who was in Sikkim as the British diplomatic representative to Tibet, received a telegram from the Tibetan prime minister passing on a complaint from the dzongpen of Shekar.

[32] It was agreed that Mount Everest might be explored but if this is used as an excuse for digging earth and stones from the most sacred hills of Tibet, inhabited by fierce demons, the very guardians of the soil, fatal epidemics may break out amongst men and cattle.

Kindly prevent officials wandering about and effect their early return.Bell knew that no precious stones had been found but he was well attuned to Tibet culture and sympathetic with it so he understood the sensitivities.