David was educated at Clifton College, and graduated M.B., Ch.B. at St Andrews University in June 1912. From November 1912 to November 1913 he filled the posts of house surgeon and house physician at the Bristol General Hospital, after holding a temporary appointment at the Royal Infirmary, Dundee. He also held the position of Medical Officer at the Claybury Asylum. David received a Lieutenancy in the South Midland Field Ambulance (T.F.) on 1st June 1913, then gained a commission at the rank of Lieutenant within the Medical Services on 30th January 1914. He joined the 5th Field Ambulance on mobilisation on 4th August 1914 but was transferred to serve as Regimental Medical Officer for the 2nd Bn. Coldstream Guards, then later the 3rd Bn. He disembarked in France on 18th August 1914. David was killed at St Julien, Ypres. Lt Shield's, R.A.M.C. wrote "Poor Rentoul the third Coldstream Guards Medical officer lay out twenty-four hours, and only died two hours before they reached him." The commanding officer of the battalion wrote "He was brave and fearless, and most gallant. He had no idea what fear was - his one idea being to assist the wounded." David was the elder son of David and Catherine Barclay Rintoul (daughter of W W Yool, J.P.) of 42 Canynge Square, Clifton, Bristol.