John Christopher (also John Cristoffel) Fleck was one of the first three land surveyors to be admitted by the Board of Public Examiners to practice in the Cape of Good Hope, in 1860. Subsequently he surveyed and mapped various farms in the Hoopstad, Kroonstad and Bloemfontein districts. In 1867 he was admitted to practice also in the South African Republic (Transvaal), even though he did not live in the territory. In 1880 he and K.J. de Kok drew up a plan of Parys. By 1877 he resided in Kroonstad, Orange Free State, where he was a partner in the firm Le Sueur and Fleck. In 1881 he was in Bloemfontein, where he succeeded G.F. Stegmann* (who left for medical treatment in England in June that year) as the second surveyor-general of the Orange Free State. He was not a progressive person in this post, but occupied it to 1897. In that year G. Baumann* took over in an acting capacity, with his permanent appointment following the next year.
Documents relating to Fleck are housed in the Miss Maynie Fleck Collection, Bloemfontein Archives Repository. He married Louise Henrietta Pronk at Potchefstroom on 22 October 1867.