The nine Viscount 800s in that list which came to BMA in early 1972 were from South African Airways.
If I recall correctly they had been advertised for sale. Mike Bishop personally travelled to South Africa with sufficient funds in place, he thought, to buy a good one. When he got there he found he was the only bidder and he managed to buy the entire fleet, plus the spares stock, with what he had arranged for just one. Presumably SAA were just glad to get rid of them.