Lieutenant-Colonel Mahon died in Ireland on 29 September 1930 aged 68.
During the South African War (1899-1902) he commanded a flying column of 2 000 men consisting mainly of South African volunteers from Kimberley, seeing action in the battles to relieve Mafeking. The town, which had been under siege for seven months by Boer forces, was facing starvation.
During the First World War he commanded the 2nd Cavalry Brigade and the 10th Irish Division during the Gallipoli Campaign.
