In retirement, he wrote a book extolling the benefits of the soya bean which was influenced by his experiences in China.

[1] He received his MB and CM from the University of Edinburgh in 1894[1] and his MD in 1897 for a thesis titled "Symptomatic and Idiopathic Insomnia: Its etiology and treatment".

[3] He married Lucy Agnes RRC in 1900 and they had one son,[1] Charles Gray, born 1909, who went on to have a distinguished career in the Indian Army.

[7] He realised they were homesick and suggested that a small Chinese pagoda be built near the entrance to the hospital which was done and painted in bright colours.

[8] In 1922, he was the British delegate to the International Finance Commission for Administration of Maritime Customs Surtax for Famine Relief.

[1] In 2022, a collection of 22 Chinese Shang dynasty oracle bones were offered for sale by a descendant of Gray.