Mahon's problem was he went beyond his remit. It does not make his observations incorrect re the airline conduct during his commission, he just wasn't supposed to say what he said.
See - The Judicial Committee of the Privy Council Decisions
The Honourable Thomas Peter Thomas Mahon v Air New Zealand Limited and Others (New Zealand) [1983] UKPC 29 (20 October 1983)
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.
Wish you'd stick to the facts
ampan. Chippendale said,
Although 2 of the pilots were shown a printout of the erroneous computer flight plan in advance of the actual flight they were not shown on a topographical map that the intended tack passed almost directly over the highest point in the area, Mt Erebus (12450 feet). Charts were carried in the aircraft on the day of the flight but these were very small scale (the largest scale was 1:3,000,000 with 1:1,000,000 insert of Ross Island) and not available to the crew until the final pre-flight dispatch planning on the morning of the departure. The 3 “maps” of the area between Cape Hallett and McMurdo which were used in the route qualification briefing all showed a track located clear of high ground and passing to the true west of the mountains as did one of he maps issued on the day of the flight. In fact the flight planned route passed to the east over very high ground instead of over the sea level ice shelf as portrayed on the briefing “maps”. One track and distance diagram issued at the route qualification briefing showed that the track from Cape Hallett was direct to the McMurdo TACAN but this did not show the location of any topographical feature.