Thomas studied at Cork and Dublin, where he qualifed in 1908, and subsequently held a resident post at Jervis-street Hospital. After a short period of private practice in Wales, he took the D.P.H., and became assistant M.O. and pathologist at Devon County Asylam, and later at Rainhill Asylam. At the outbreak of war Thomas resigned the last post to join the R.A.M.C. He entered the war in Egypt in March 1915 and served with a Casulaty Clearing Station in Gallipoli and France before becoming attached to the Royal Fusilliers. Thw war diary of the 2/Royal Fusiliers records Capt T Fehily as the MO wef c18 March 1918. On the 10th April 1918 he was in the Merville area and moved forward to Estaires. The war diary noted him as being killed in action on the 14th April 1918, (Bn lost 7 other officers killed and 7 wounded/missing) . CWGC shows him as died 13 April 1918, he is also recorded as being killed in action on the 13th April in Officers Died. Thomas was the son of Patrick and Margaret Fehily of Ballineen, Co. Cork [Information from the 2/Royal Fusiliers war diary kindly provided by James Munden]