John, a British citizen, was born in South Africa and educated in England at Eton. He joined the British Army in World War II, and served as one of the youngest commissioned officers in the Rifle Brigade in Northwest Europe and, later, in Kenya during the Mau Mau troubles. His military service included periods with Intelligence. He retired from the Army in 1956 and joined IBM United Kingdom, serving on its Board of Directors. He was a leader in public and community affairs and helped to develop many national and international educational and community organizations.

In 1976 he retired from IBM and resigned from a number of other director-ships, as well as political, educational, and voluntary appointments, to give his full time to the practice of Christian Science. He was first listed as a practitioner in the Christian Science Journal in 1979 and maintained a worldwide practice. John contributed many articles to the Christian Science periodicals and served on the Christian Science Board of Lectureship. He was a member of First Church of Christ, Scientist London where he served as First Reader.