Educated at Eton and Sandhurst, he entered the Scots Guards as a cadet, and was promoted to second lieutenant on 21 February 1900.
[4][5] Following the end of the war in June 1902 he returned with most of the men of the guards regiments on board the SS Lake Michigan, which arrived in Southampton in October 1902.
[9] He resigned his commission on 6 March 1909, after his father succeeded to the earldom and he became heir apparent; his uncle John, then a lieutenant in the Guards, was promoted captain in his place.
A recording that his daughter, Lady Silvia, made at the age of 90 recounting the history of Holkham Hall is a British Library exemplar of the conservative received pronunciation accent of English.
(Colonel Trefusis was the son of the 19th Lord Clinton and Lady Mary was the daughter of the 5th Duke of Buccleuch).