There was a revisionist biography by JDF Jones, which came out in 2001, that suggested that van der Post was often selective with the truth about his exploits. Despite the fact that he was actively involved in the anti-apartheid movement he hated Mandela, seeing him as a hindrance, and consequently may have set back the cause by some years. So, 'old fraud' is a bit harsh, and 'somewhat less than straight up' may be nearer the mark.