Two examples of what a dope Mahon was: (1) Of the most significant lines in the CVR transcript was "Very hard to tell the difference between the cloud and the ice." That line was never referred to in the report, or even the subsequent book.
(2) Faced with indisputable evidence that the waypoint conveyed at the briefing was at McMurdo Station, Mahon had this to say: "The pictorial representations showing the observers that the flight path was down McMurdo Sound and these displays would, not unnaturally, take precedence over the spoken words indicating a direct track from Cape Hallett to McMurdo Station and indicating the NDB co-ordinations as the destination waypoint." (p60)
There are so many mistakes in that one single paragraph that I'm only going to identify the worst, which is that pilots would silently sit through a briefing, receive contradictory information, and then make there own decision about which would "take precedence." Ian Gemmell was right: Mahon was an idiot.