Tom did his medical training at St Thomas Hospital, qualifying L.S.A. in 1879 and M.R.C.S. in 1880. He took up a commission in the Army Medical Services as Surgeon Captain on the 5th February 1881, then gained promotion to Major on 5th February 1893. From 1899-1902 he served in South Africa, during which time (on 5th February 1901) he was promoted to the rank of Lieutenant Colonel. Further promotions include the rank of Brevet Colonel, which took place on 28th April 1909; the rank of Colonel, which took place on 17th November 1909, and the rank of Surgeon General from the 14th July 1914. Before war broke out he held the appointment of Deputy Director of Medical Services (A.D.M.S.), Aldershot. On 5th August 1914 he was re-appointed as Director of Medical Services (D.M.S.) of the Expeditionary Force, and was mobilized with General Headquarters in London. He proceeded to France from Southampton on the 9th August 1914 with his staff, disembarking at Havre the following day. He opened a camp office at Havre until the 13th August, when it was moved to Amiens. During the period of concentration his work was mainly directed towards obtaining suitable sites for hospitals on the lines of communication, arranging for the distribution of those units not under instructions to open on arrival and organizing the means for the evacuation of sick and wounded. On 15th October 1914 he, and the staff of the line of communication moved to Abbeville. At the end of December, when the five army corps and the Indian Corps were grouped into two army commands and the whole of the administrative medical service was reorganized, he ceased to be D.M.S. of the force, and became D.M.S. of the lines of communication. His responsibilities changed to include the control of all medical services on the lines of communication, including the Marseilles base and southern line. He was appointed Companion, Order of the Bath (C.B. [mil]) in 1915; Knight Commander, Order of St. Michael and St. George (K.C.M.G.) and Commander of the Order of the Crown (of Belgium) in 1917. He was also awarded Croix Commander, Legion of Honour (L.G. 24/2/1916) for his service in overlooking the evacuation chain during the Retreat. He was due to retire on 10th August 1917 but was retained on the Active List. He did retire in December 1917, when the Army Council decided to place on the retired list all the officers who had reached the age for compulsory retirement.