Sir John was medically trained at Guy's Hospital, qualifying M.R.C.S., L.R.C.P. & M.B. in 1901, and F.R.C.S. in 1903. He then held House Physician, Assistant House-Surgeon, and Clinical Assistant appointments there. In 1920 he became a Trustee of King’s College of Household and Social Science. Sir John first served with the British Army during the South African War, on the staff of the Imperial Yeomanry Hospital. On the outbreak of war in August 1914 he was given an honorary temporary commission at the rank of Colonel with the Army Medical Services on becoming the personal medical officer to Sir John French, later Earl of Ypres, Commander in Chief ,and his staff whilst in France. He was later appointed Assistant Director General of Army Medical Services and of Deputy Director of Medical Services in Great Britain. During the war he had became a member of the experiments committee with the British Army in the Field, along with the anti-gas committee, and with the Central Medical war committee. In 1916 he wrote on chemical warfare and on the defence against gas attacks and gas-proof dug-outs. He was mentioned in dispatches four times, and was created C.M.G. in 1916 and K.C.M.G. in 1919. After the war, and up until he retired, he took up many appointments with the University of London. For recreation, he enjoyed fly-fishing. He was the youngest son of William Atkins of Norwich, and the husband of Elizabeth May (daughter of James Davies Smith). They were married in 1904.