John received his medical education at the Westminster and London Hospital, having won an entrance scholarship and the Abrahams prize in clinical pathology. After qualifying L.M.S.S.A. in 1914 he became an assistant house surgeon and surgical registrar at the hospital, then served as house surgeon at the Leicester Royal Infirmary. On 19th August 1914 he joined the R.A.M.C. Special Reserve, at the rank of Lieutenant, and was mobilized for war service on the 19th September 1914. He entered the war in France on 18th March 1915. After being promoted to the rank of Captain on 1st April 1915, he was posted to serve with the 1st Field Ambulance. He joined them in the field, arriving on the 7th April, from the Base. On the 9th April he became part of a Bearer Division for the unit, and on the 10th May a circular memo from GOC, 1st Division was sent out highly praising his work, along with others, for recovering and treating many wounded. John also spent some of his time with the unit being transferred for temporary duty to various regiments within the Division to relieve the Regimental Medical Officers for temporary leave. On 5th July 1915 he was transferred as RMO to the 39th Brigade, Royal Field Artillery and was taken off the strength of the 1st Field Ambulance. John remained in France until 1916, then later in the year studied and qualified as M.B., B.S. On 1st January 1917 he took up a permanent regular army commission, with the R.A.M.C. at the rank of Lieutenant (temporary Captain), and later that year served with the East African Expeditionary Force. From 1918 to 1919 he was stationed in South Africa. In 1921 he became a Master of Surgery. He also qualified F.R.C.S. on 9th June 1921, and was promoted to the rank of Captain on 19th August 1921 (backdated to 19th April 1920). From 1923 to 1925 he served in India, then retired with gratuity on 5th August 1925. The following year, 1926, John received with distinction the certificate of the London School of Tropical Medicine, and in the same year graduated M.D. in tropical medicine at the University of London. From 1926 he became a Medical Officer in the Malayan Medical Service, up until 6th December 1929 when he took up an appointment with the Indian Medical Services. He joined at the rank of Captain, being promoted Major on 20 July 1932. He went on active service in Burma at the beginning of the Second World War but died of illness.