He was promoted to lieutenant on 9 October 1899,[5] and served with his regiment during the Second Boer War from 1899 to 1901, where he was present at the engagements at Belmont, Enslin, Modder River, Magersfonstein, the relief of Kimberley, and the advance to Bloemfontein and Pretoria.

[8] After leaving the army, Hamilton-Temple-Blackwood was appointed military secretary to the Governor General of Australia, Sir Ronald Munro-Ferguson (later Viscount Novar), who was his brother-in-law.

Following the outbreak of the First World War, he rejoined his old regiment, the 9th Lancers, and was seriously wounded while serving on the Western Front in October 1914 and was subsequently transferred to the Grenadier Guards.

They had two children:[8] On 21 July 1930, Lord Dufferin was flying with a party of friends from Berck, a small village in France near Le Touquet, back to England when the aircraft crashed outside Meopham, Kent, killing all those on board.

; Viscountess Ednam, the wife of Viscount Ednam (heir to the Earl of Dudley) and a daughter of Cromartie Sutherland-Leveson-Gower, 4th Duke of Sutherland; and Mrs Loeffler, a well-known society hostess, along with the pilot, Lt. Col. George Lochart Henderson and the assistant pilot, Mr C. D. Shearing.