Fanshawe served throughout the Boer War, where he received a brevet promotion to lieutenant-colonel and was mentioned in despatches twice; following the war, in 1903, he was confirmed in his promotion to lieutenant-colonel and given command of the Queen's Bays.
Fanshawe served throughout the second Boer War, where he received a brevet promotion to lieutenant-colonel and was mentioned in despatches twice (including by Lord Kitchener dated 23 June 1902). Following the war, in 1903, he was confirmed in his promotion to lieutenant-colonel and given command of the Queen's Bays.