The Ou Tronk initially consisted of 5 long World War 2 wooden barracks, a kitchen and ablution facilities. It was converted to a Medium Security Prison in the 1950s. In the 1960’s eight new plastered brick buildings were built as a temporary MSP.
Common law and political prisoners were housed in the Ou Tronk while they quarried, excavated and chopped stone for the building of the permanent MSP. In 1962, Nelson Mandela was imprisoned in the Ou Tronk for a few weeks. After the Rivonia Trial in 1964, he and six of the trialists were imprisoned in the B section for two weeks until the isolation block of the MSP was completed.
The Ou Tronk was converted to workshops when hard labour ended in the mid-1970s. Prisoners were trained in building, plumbing, carpentry and such craft and trades in these workshops. The wooden WW2 barracks of the Ou Tronk were demolished in the 1990s. Today the only reminders of the Ou Tronk are the bare concrete slabs.