Finlayson entered the British Army from the Suffolk Militia and was commissioned into the Royal Artillery as second lieutenant on 17 March 1900.[2] He was promoted to lieutenant on 3 April 1901, and was attached to 131 Battery of the Royal Artillery, stationed at Chatham.[3] Seconded to serve with the Imperial Yeomanry during the Second Boer War in South Africa from 25 April 1902,[4] he received the temporary rank of captain serving in the 24th battalion, Imperial Yeomanry.[5] He vacated his appointment with the Imperial Yeomanry on 1 August 1902,[6] and returned to the Royal Artillery.[7]
After the war Finlayson was Deputy Commander, North Russia Forces, a post he held from 1918 to 1919.[2] He then became an instructor at the Senior Officer School in 1919 before attending the Staff College, Camberley and being appointed Military Assistant to Chief of the Imperial General Staff in 1921.[2] He went on to be a General Staff Officer at the War Office in 1922 and joined the Staff College in 1925.[2]
Finlayson was churchwarden of St Mary's Church, Kersey and a memorial was erected in his memory in the church.[11]
Family
Finlayson was married to Mary Leslie Richmond and together they had two sons, Air Vice Marshal James Richmond Gordon-Finlayson,[12] Major-General Robert Gordon-Finlayson and a daughter, Mary Leslie, who married to become Mary Boyle, Countess of Cork.[13]