Coghlan was elected to the Kimberley town council in 1897. The following year Colonel Frederick Schermbrucker's youngest daughter Gertrude Mary Schermbrucker, described as an attractive and sociable woman, arrived to stay at the house Coghlan shared with his sister and mother. Coghlan married Gertrude in Wynberg, a southern suburb of Cape Town, on 10 January 1899. Around this time Coghlan's friend Percy Ross Frames invited him to join him in Bulawayo, one of the main settlements in Rhodesia, as Matabeleland, Mashonaland and the adjoining areas were now collectively called. Coghlan was receptive to the idea, but was compelled to stay in Kimberley by the outbreak of the Second Boer War in October 1899. Kimberley was besieged by Boer forces, cut off by rail and telephone, from 14 October until its relief by General John French on 15 February 1900.