[1] Gass was educated at King's School, Bruton, and then later obtained degrees at both Queens' College, Cambridge and Oxford University.

During World War II Gass entered the Army and achieved the rank of Major, he served in East Africa and Burma with the Gold Coast Regiment of the Royal West African Frontier Force (1939–1945); he was twice mentioned in despatches.

After the war he returned to the Service, spending three years in Ashanti and two in Ghana before being posted in 1958 to the West Pacific High Commission as Chief Secretary.

During the disorder, Governor Sir David Trench happened to be absent from Hong Kong and all of a sudden there was no one fully in command of the government.

During the riots, he took a tough stance against the activists, to effectively control the situation, but has also become one of the main targets of attack leftist camp vocal opposition.