NavList:

Brad Morris you wrote: I did encounter the grid referenced to meridian lines in the 1949 text.  They indicated that the grid was made by drawing a line parallel to the 0 to 180th meridian.  The direction away from the North Pole along the 180th meridian is "grid north".   

It’s called the Greenwich Grid.  It was invented by Wg Cdr Kenneth C Maclure DFC RCAF whilst Oi/c Testing and Development at the Empire Air Navigation School (EANS) at RAF Shawbury in 1944/45.  The technique was first used on the pioneering RAF trans-polar flights in the Aries Lancaster (Man is not Lost - Dickie Richardson p 258).  You can find Maclure’s paper here: Maclure, Wing Commander K. C., "THE ARCTIC FLIGHTS OF THE LANCASTER "ARIES," MAY 1945", NAVIGATION, Journal of The Institute of Navigation, Vol. 1, No. 1, 1946, pp. 3-7.  I’m struggling read it through the RIN website, so I'm not sure how much it describes the grid, but IoN members can get it through theirs https://www.ion.org/publications/abstract.cfm?articleID=102141 .
The technique was still being taught when I completed the Staff Navigator Course in 1973.  I could try and make some sense of my hand written notes at the time, but far better to read about it in Ch14 of the US Flight Navigator Manual available on-line here https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/  .  DaveP