In order to meet South African demands for a greater share in the running of the mail service, the "Transvaal Castle" and her fleetmate RMS "Pretoria Castle" (respectively the youngest and oldest units of the fleet) were transferred to the South African Marine Corporation (Safmarine) in 1966. The "Transvaal Castle" was taken over by Safmarine on 12 January 1966 and renamed "S.A. Vaal". The ship's hull was repainted white and her funnel changed to Safmarine's mid-grey, with three thin lines of the then South African national colours: orange, white and blue. Although now under Safmarine ownership, both ships were bareboat chartered back to Union-Castle and continued to be manned by the same crews as the other mail ships. RMS "S.A. Vaal" remained registered in London and continued to operate on the same service as before. Thus the UK—South Africa service became a joint operation between Union-Castle and Safmarine. In February 1969 the "S.A. Vaal" and "S.A. Oranje" were re-registered in Cape Town. but continued to be managed and crewed by Union-Castle, with a few Safmarine officers in later years. The mail ship operation was always managed from London.