Son of Dr Robert McDonnell M.D., F.R.S., of Dublin and Susan, daughter of Sir Richard Bolton McCausland, Recorder of Singapore. He came to Winchester from Dunchurch Hall. He went to King’s College, Cambridge in 1897 and took his degree in Mechanical Science.
The year he left the School he joined the 5th (Militia) Battalion of the Leinster Regiment and served with them during the South African War. In August 1914, he was called up and for the greater part of the war served on the staff at Queenstown in Ireland. After some months in command of his old battalion, he was sent in August 1918 to join the 1st Inniskilling Fusiliers in France. He fell in action near Ypres on September 29th 1918.
- Surname: McDonnell
- Forenames or initials: John
- House: F
- Years in School: 1892-1897
- Rank: Lieutenant Colonel
- Regiment: Leinster Regiment
- Date of Birth: 2nd November 1878
- Date of Death: 29th September 1918
- How Died: Killed in action
- Location in War Cloister: Outer A1
- Decoration: NA
- Burial Site: YPRES RESERVOIR CEMETERY: Grave II.D.32