Thomas Gilbert was born in Purley, Surrey, England, son of Charles William Gilbert, medical practitioner, and Lilian Mary (née Measures). He was educated at Mayfield, England, and Albany High in Western Australia and attended the faculty of medicine in the University of Melbourne from which he graduated with honours in 1929. After a year as RMO at St. Vincent’s Hospital Melbourne (1930), and a year as RMO at Queen Mary’s Hospital Stratford London (1931), in 1932 he was a senior medical officer with the London County Council Hospitals, Dartford and Mile End. He also spent time as a clinical assistant in the dermatology departments of St. Paul’s Hospital and St. John’s Hospital, London. He married Mabel Mary Palmer in 1934 and subsequently they had three sons and five daughters.

Between 1933 and 1940 he conducted a general practice in Perth and was an assistant at the Perth Hospital from 1935 to 1938. He served in the AAMC as a dermatologist/ physician from 1941-46 and from 1942-44 with 118 AGH, with a year overseas in 1945 with 2/12 AGH, having achieved the rank of Major in 1943. In 1946 he was Officer in Charge of the Medical Division of 110 Perth Military Hospital. He was with the Repatriation Medical Service from 1946-66, as a hospital administrator, and from 1960 to 1966 he was the medical superintendent of the Repatriation General Hospital, Hollywood, WA.

In 1946 he published two papers: Gilbert TM and Cox CB Colloid degeneration of the skin: report of eight cases Med J Aust 1946 2 21-2; Gilbert TM and Hing SR The Stevens Johnson syndrome Med J Aust 1946 2 774-6.

He was appointed as a Justice of the Peace, Western Australia in 1934 and his wide range of interests included collecting native plants as well as paintings and objects d’art, reading all forms of literature, swimming and tennis.