Kingsmill was educated at Trinity College, Dublin, where he gained a scholarship in 1897, and then graduated B.A. in 1898; M.B., B.Ch., and B.A.O. in 1901, and M.A., M.D., and D.P.H. in 1903. He held appointments of resident medical officer at Cork Street Fever Hospital, Dublin, and of house-surgeon at the Swansea General and Eye Hospital, he then went into practice at Ardwick, Manchester, and in 1913 was elected member of Manchester City Council for Ardwick Ward. He took a commission at the rank of Lieutenant with the 3rd East Lancashire Field Ambulance on 11th February 1912, and was still on their officers list in Januray 1917. He disembarked for service overseas on 9th September 1914. According to his MIC, Kingsmill served with the 18th Field Ambulance and 39th Stationary Hospital. He received the Distinguished Service Order "For conspicuous gallantry and devotion to duty at Hooge. During the entire night of 9 - 10 Aug 1915, and the whole of the following day and night, he was attending to and evacuating wounded from the front trenches, time after time exposing himself to shell and rifle fire. He was twice slightly wounded, but stuck to his work with unflagging energy. It was entirely owing to Capt Jones that the crator was successfully evacuated of wounded." Kingsmill was wounded again in September, 1916, and was later severely gassed. He was killed whilst serving as the medical officer for the 1st Bn. East Kent Regiment (The Buffs). He was the son of Percival and Margaret Jones of Dublin