Haig-Brown matriculated at Pembroke College in 1896 and graduated with a B.A. in Classical Tripos in 1899. He was Commanding Officer of the OTC at Lancing College and was interested in the Junior Division of the OTC movement. During the First World War Haig-Brown fought on the Western and Italian fronts between 1916 and 1918. He was mentioned in dispatches twice and awarded the Distinguished Service Order. He was killed by machine-gun fire in France on 25 March 1918. Prior to the War he authored 3 books.