I'll always remember an experience with a very senior Training Captain in a 777 heading over Greenland on our way over the Pole. I used to use route 2 to put the DME arc's to the ILS into Thule. When performing the handover brief he asked why on earth I would do such a thing. My response was so that in the event of a scenario where the S/O would have to fly the approach, they could use LNAV on the DME arc to the LOC. Now, I may have been wrong, and I was always keen to learn if someone had a different approach to doing things but He BLEW UP at me. "YOU CANNOT USE LNAV IN THE POLAR REGION" was screamed across the flight deck (as we continued to fly in LNAV). Once I had shown him the correct FCOM procedure regarding TRU/MAG switching and LNAV he proceeded to take his pen and draw a line through it, claiming that when he was in the military they flew real Polar nav and this procedure is dangerous. I found several of the FCOM's on aircraft further down the line that had the same line on the same page, it had obviously become quite a habit for this guy.