Thomas Elmhirst was born on 15 December 1895, the 4th son of the Reverend W. H. Elmhirst, of Elmhirst, near Barnsley, Yorkshire. He was educated at the Royal Naval Colleges at Osborne [Isle of Wight], 1908 and Dartmouth [Devon], 1910. In 1930 he married 1st, Katharine Gordon (who died in 1965), 4th daughter of William Black, of Chapel, Fife [Scotland]; they had one son and one daughter. In 1968 he then married (2nd), Marian Louisa, widow of Colonel Andrew Ferguson and daughter of Lieutenant-Colonel Lord Herbert Montagu-Douglas-Scott.

In April 1912, Elmhirst joined his first ship, HMS Cornwall. He transferred to the Indomitable in May 1913 on becoming a midshipman, seeing action at both the Dardanelles and the battle of the Dogger Bank in early 1915. On 17 March he then moved to the Royal Naval Air Service, to qualify as an airship pilot, becoming acting sub-lieutenant on the North Sea anti-submarine patrol in May 1915. By 1917 he was promoted to flight lieutenant and by March 1918 to major, commanding the Naval Airship Patrol Station at Anglesey [Wales].

Following the war, Elmhirst joined the Air Ministry in 1919, moving to the Howden Airship Station for a brief time in 1921, before becoming commander of the Malta Flying Boat Flight in June of that year. He returned to Britain in 1925, working at both the RAF Staff College and the Air Ministry, Intelligence Section, before taking up flying duties again in January 1929 as Squadron Leader and Staff Officer at Leuchars [Fife, Scotland]. In the following year, Elmhirst went back to Malta to serve on the Air Staff, then in 1934 became S.N.O. on the War Course, Greenwich [London]. He reformed No. 15 (Bomber) Squadron in July 1934, commanding this and the Abingdon Wing, (1935-37) before becoming 1st British Air Attache to the Embassy in Ankara [Turkey] in February 1937. In May 1939 he was recalled, taking up the post of Bomber Station commander at Leconfield [Yorkshire], but in January 1940 returned to the Air Ministry as Deputy Director of Intelligence.

During the Battle of Britain Elmhirst served as Air Commodore in Fighter Command, but in December 1940 was sent back to Turkey as RAF member of the British Mission for Staff conversations with the Turkish General Staff in Ankara. He then took on the job of Air Officer Commanding RAF Egypt in 1941 (being mentioned in despatches twice), then 2nd in Command of the Desert Air Force during the El Alamein campaigns in Egypt in 1942. In February 1943 he became Chief of Administration, first for Algiers, then in November for the 2nd Tactical Air Force in North West Africa, (he was mentioned in despatches and awarded the CB for the Tunis and Sicily campaigns). Leaving the Middle East, he served as 2nd in Command of the British Air Forces in North Western Europe during the campaign in Normandy [France] and Germany, 1944-45 and was made Air Vice-Marshal in November 1944 and also awarded the KBE. At the end of the war, Elmhirst became Assistant Chief of Air Staff (Intelligence), 1945-47, then Chief of Inter-Service Administration in India in 1947. He was the first Commander-in-Chief of the Indian Air Force, from 1947 until his retirement in 1950 and was then made an Honorary Air Marshal in the Indian Air Force.

Following retirement, Elmhirst worked as the Civil Defence Controller Eastern Zone for Scotland, 1952-53, and was the organiser of Operation Totem (the detonation of the second British atom bomb) in January 1953. He ended his public career as Lieutenant-Governor and Commander-in-Chief of Guernsey, from 1953 to October 1958. Elmhirst died on 6 November 1982.