Seymour served throughout the South African War and received the Queen's South Africa Medal with five clasps.
In April 1913, Seymour, then of the Royal Dublin Fusiliers, was appointed adjutant of the 25th (County of London) Cyclist Battalion of the London Regiment,[REF] in which posting he continued until 1916, before returning to the Royal Dublin Fusiliers to take command of its 10th Battalion.