Guy Spearman Armstrong was born in Westville, Wyke Regis, Weymouth, Dorset, the son of Charles Spearman Armstrong (1847–1924), Irish-born pioneer of tea and cinchona in British Ceylon and author of “Tea Cultivation in Ceylon” (1884).
Commissioned 2nd Lieutenant from O.T.C. Cadet on 13 Jan 1915, Armstrong entered France on 19 Mar 1915 with the 1st Battalion.
Armstrong was last seen alive in action at Hill 70 near Loos and reported missing on 27 Sep 1917.
His body was found a few days later by search party.
He is buried at Dud Corner Cemetery, Loos-en-Gohelle, Pas de Calais, Hauts-de-France and remembered on the West Byfleet Memorial, Chertsey, Surrey.