He was a significant influence on safety regulations in factories and mines, and was an original member of the League of Nations' Opium Advisory Committee.

[1] He had strong religious convictions, privately held, which informed his public stance on worker's safety, narcotics and child welfare.

[2] In 1892, at the age of 24, Delevingne passed the civil service exam for clerkships and took his first job at the Local Government Board.

[3][4] Though Delevingne was involved with many aspects of the Home Office, he was particularly concerned with occupational health and safety, with special focus on regulations for factories and coalmines.

[6] In his 1950 obituary, The Times wrote that Delevigne was "undoubtedly an unobtrusive, but powerful, force behind much of the factory legislation that was passed during the first quarter of the present century.

He believed that the key to narcotics control lay in curbing their supply and that the drug trade was "a great evil which must be fought.

As one of the Undersecretaries of State at the Home Office, Delevingne represented the United Kingdom's interests on the League of Nations' Opium Committee from 1931.