There are a few points raised in the above posts that warrant comment.
ampan - excellent post #1244. I wasn't aware of this discrepancy in Mahon's espousings, but it's actually pretty huge. Just another example of how he was blinkered, and brainwashed himself when confronted with evidence that didn't support his staunchly held mantra that the crew were blameless.
The Beaufort island issue has not been given the attention it deserves. It is inconceivable that Collins and Cassin didn't see it. They were flying VFR. Part of flying VFR is to identify significant geographical landmarks, and an island of 2500' elevation (when you're intending to fly even lower) would surely qualify - not just adopt some "meh, whatever" attitude, which seems to have been what occurred.
Which brings me on to poor Peter Mulgrew. He was employed by the airline to commentate to the passengers. Nothing more. In fact, unless he had flown around the area more than once before, he wouldn't have been able to identify much from the air at all. I remember from my PPL days how long it took me to reliably identify from the air geography I'd known all my life. Identifying landmarks was the job of the pilots, not Mulgrew. But he is often written about as if he were an integral member of the flying crew. He wasn't. Nothwithstanding the posthumous relevance of some of his comments on CVR, his input into the conduct of the flight should have been zero.
Which is why Collins's query to Mulgrew if he could "get them out over the Wright valley" is gobsmacking. The mind boggles as to what scenario Collins was envisaging - him hand flying VFR with Mulgrew over his shoulder saying "left here, and then if you hop over that rise you should be in a valley........."
This is actually starting to make me feel a little angry. People who believe that the crew are blameless get there through a combination of multiple assumptions and invalid reverse self-fulfilling logic. It stinks.