Following the outbreak of the Second Boer War in late 1899, Colvin was on 7 February 1900 appointed Deputy-Assistant Adjutant-General in the Imperial Yeomanry, responsible for corps raised outside the headquarters of the existing yeomanry regiments.[3] With the expansion of the number of Imperial Yeomanry regiments, he was a month later, on 14 March 1900, reassigned and appointed in command of the 20th Battalion, Imperial Yeomanry,[4] which set out for South Africa later that month. He was promoted to lieutenant-colonel on 8 November 1901, and transferred to the Essex Yeomanry. For his services during the war, he was appointed a Companion (military) of the Order of the Bath (CB) in November 1900.[5] After the end of the war, he received the honorary rank of colonel.[6]
He was later awarded the Companion (civil) of the Order of the Bath (CB) in 1911, and was promoted to a Knight Commander of the Order (KCB).
Covin married, on 26 June 1895, Lady Gwendoline Audrey Adeline Brudenell Rous (1869–1952), daughter of John Rous, 2nd Earl of Stradbroke and Augusta Bonham.
They had two children:
^Craig, F. W. S. (1989) [1974]. British parliamentary election results 1885–1918 (2nd ed.). Chichester: Parliamentary Research Services. p. 276. ISBN0-900178-27-2.
^Craig, F. W. S. (1983) [1969]. British parliamentary election results 1918–1949 (3rd ed.). Chichester: Parliamentary Research Services. p. 351. ISBN0-900178-06-X.
^"Births". The Times. No. 36092. London. 17 March 1900. p. 1.