[1] Colston was an officer in the 4th (Militia) battalion of the Prince of Wales's (North Staffordshire Regiment).

He was commissioned a second lieutenant in the Grenadier Guards on 21 February 1900,[2] and served with the 2nd Battalion in South Africa 1901–02 during the Second Boer War, where he was wounded.

Following the end of the war, he returned home with other men of his battalion on the SS Galeka in October 1902.

[4] During World War I Colston was in the Retreat from Mons, the Battle of the Marne and the fighting on the Aisne before he was wounded and invalided back to the UK.

Colston was promoted to Brevet Lieutenant-Colonel in 1917 and appointed to command 233rd Brigade in the rank of Temporary Brigadier-General.

He retired from the Army with the honorary rank of Brigadier-General in 1932, and was appointed Exon of the Yeomen of the Guard, receiving his stick of office from King George V.[4][6] During World War II Lord Roundway served as Zone Commander of the Wiltshire Home Guard.

[1][7] After an illness of several months, Lord Roundway died on 29 March 1944 when in the absence of male heirs the Barony became extinct.