We are something of a ‘divided’ household when it comes to the Inklings: I’m a CS Lewis fan, my husband is very much a Tolkien fan. That’s not to say that we don’t read both, more to say where preferences lie. Whichever you prefer, the original illustrations for Lord of the Rings and Narnia are in the same style, having been done by the same artist.
The map in question was actually found among the books of the artist, Pauline Baynes. The Guardian has a good write up on the map, which you can find here. You’ll also want to make sure you check out the write up from Bodleian about the acquisition– it includes a picture of the map as well as the post map that Baynes illustrated in 1970.
I was in Oxford once, though it was only for about 2 hours so I wasn’t able to go really anywhere that I wanted to. For those who have been, did you see anything from the Tolkien collection? Or any of the other special collections?