Mansergh D. Robinson began working for the Cape Government Railways in February 1899. From 1903 to 1906 he was stationed at Indwe, Eastern Cape, then in Cape Town (1907) and later in George (1909). He was a member of the newly established Cape Society of Civil Engineers in 1903 and in 1910 served on its council. During these years he contributed two papers to the society's Minutes of Proceedings: "Notes of the erection of Tsomo River Bridge" (1905, Vol. 3) and "Railway transition curves" (1909, Vol. 7).
In August 1910, a few months after the formation of the Union of South Africa, Robinson was appointed as new construction engineer in the South African Railways and Harbours, stationed at its headquarters in Johannesburg. At this time the Cape Society of Civil Engineers changed its name to the South African Society of Civil Engineers. Robinson remained a member of the society, served on its council for at least 1913, and was elected president for 1918. He was also elected a member of the (British) Institution of Civil Engineers in about 1910.
At his death in 1934 he was survived by his wife, Norah Robinson.