I recently acquired the cover shown in the attached scans because I though the dual Boer/British censorship unusual. Since this is not my area, my thoughts are not particularly relevant -- so I am posting it here in hopes that someone in the know can enlighten me.
It was posted on 31 January 1900 from Johannesburg, which the British did not occupy until 31 May 1900. That it got through the lines (and quickly at that) is attested to by the 7 February 1900 Durban backstamp.
Two questions arise:
1) How did this cover get from Johannesburg to Durban?
2) Is such dual censorship uncommon or have I just been inattentive?