 During the First World War Hylton-Stewart was commissioned in the British Army and served with school Officers' Training Corps (OTC), first at The Leys School and then at Haileybury.He remained with the Haileybury OTC until 1929 when he resigned his commission.Hylton-Stewart did not return to first-class cricket after the First World War but played Minor Counties cricket for Hertfordshire up to 1927.