Twisleton-Wykeham-Fiennes was gazetted into the 108th Foot of the Oxfordshire Militia on 22 January 1879, the date of the Battle of Isandlwana. His father, who was anxious for his eldest son to see active service in the Anglo-Zulu War, had him transferred to the 2nd Battalion of the Royal Scots Fusiliers, and he was sent to South Africa to "avenge" the massacre at Isandlwana. Twisleton-Wykeham-Fiennes acted as secretary to Sir Henry Bulwer, then the Governor of Maritzburg, and accompanied the column that captured Sikukuni. The next year, he joined the 1st Battalion of his regiment at Secunderabad, British India, and returned to England eight months later. He was promoted to captain in 1887. In 1890, he made adjutant of the 3rd Battalion, of which he was later to be Hon. Colonel, and retired in 1899. On 2 June 1902, he was appointed Lieutenant-Colonel in command of the 3rd Battalion of the Royal Scots Fusiliers, based in Ayr. He was appointed an Honorary Colonel of the Battalion in 1907. During the First World War, he served as an Area Commandant in Flanders. He was also a Lieutenant-Colonel in the 3rd Battalion of the Middlesex County Regiment.
Business and political career
After retiring from the Army in 1899, Twisleton-Wykeham-Fiennes entered private industry, spending the next few years as a salesman for a well-known brewing firm. He travelled frequently to South Africa, Malta, and Mediterranean stations occupied by British troops. In 1907, he succeeded his father in the barony and entered the House of Lords, where he was a staunch Liberal. He promoted a School Attendance Bill and a Bill dealing with the abuses of the traffic in worn-out horses. From 1912 to 1915 he served under H. H. Asquith as Comptroller of the Household. He was an active member of the Home CountiesLiberal Federation, and was chairman of the National Land and Home League. He was also on the Standing Joint Committee of the Oxfordshire County Council, and in 1930 he became High Steward of the City of Oxford.
Family
Lord Saye and Sele married Marion Ruperta Murray, daughter of Major Robert Bartholomew Lawes, on 20 February 1884. They had five sons and two daughters:
Geoffrey Rupert Cecil Twisleton-Wykeham-Fiennes, 19th Baron Saye and Sele, died unmarried
Ivo Murray Twisleton-Wykeham-Fiennes, 20th Baron Saye and Sele married Hersey Cecilia Hester Butler, daughter of Capt. Sir Thomas Dacres Butler, and had issue
Evelyn Idonia Twisleton-Wykeham-Fiennes
G. Capt. Hon. Laurence John Evelyn Twisleton-Wykeham-Fiennes, died unmarried
Ingelram Robert Nathaniel
Hon. Allen Rupert Ingelram Twisleton-Wykeham-Fiennes , killed in a motorcycle accident
Hon. Cicely Marion Violet Joan Twisleton-Wykeham-Fiennes, married John William Dunne, son of Gen. Sir John Hart Dunne
He died at the family seat of Broughton Castle in Oxfordshire in February 1937, aged 78, and was succeeded in the barony by his eldest son, Geoffrey. Lady Saye and Sele died 27 July 1946, aged 82.