An interesting thread
I joined BOAC from Hamble in '67 and due to no pilot courses we spent the first summer doing some of the Nav course - 6 weeks in Braincrank then let loose on the Atlantic - under supervision of course. Most of the time it was back and forth to Bermuda with the occasional Toronto and JFK.
Bermuda was off the track system but the others weren't - certainly the lateral separation was 120nm - along track I think was 20mins at the same Mach number, but just about everybody flew at .82.
At the end of the summer we were given our pilot courses and having spent the summer on the 707 we were given the VC10 - similarly those who nav'd on the VC10 were given the 707! A quick visit by a number of us to the VC10 flight manager - the lovely Norman Bristow soon got that changed!
Regarding the polar operations many moons later I was a Nav Instructer and found myself doing lots of ANC trips using the grid nav system others have mentioned. Actual navigation was fairley easy - quite a few NDB's and use of the weather radar to pick up some of the more recognisable landmarks.
We normally only went as far north as 80N but early 72 - 17th Jan. to be exact - Canadian ATC were on strike so we had to crawl up the FIR boundary to the North Pole and the south to ANC. AS far as we know that was the first BOAC aircraft actually to fly over the Pole. Wish I had pulled the chart and Nav log from the archives before they were destroyed.
INS's came a few years later and a command a couple of years after that!