Alan Lee illustration of Pelennor Fields

I wonder if it was a deliberate choice to reverse it to make the positioning of the sky with the oval more aesthetic? Hard to see any reason other than - presumably - the graphic designer working on the book thought it worked a bit better.

The original image (meaning the illustration itself, not the cover) is not reversed, though it remains to be seen if 'flipping' was intentional or not. As Stu said, perhaps it was done to 'work' better as a cover.

This question came up before over on Facebook, and I asked:

Alan Lee:

I can vaguely recall that the illustration had been reversed in that earlier edition. Perhaps it was something to do with the placement of the title? But, yes, the horse on the banner should be looking to the right.

HarperCollins:

the current presentation of the ROTK painting is correct. The centenary set predates my stewardship so I’m unaware whether the flipped version was intentional or accidental.

It is not immediately obvious that the image is reversed, wonder if it was just a mistake by the designer who did not notice that it was reversed, but it sounds like we will never know. An interesting oddity though.

I like the theory positing that the image was reversed for the cover, in order to make the layout fit with the title - but, as you say, there is no-one obviously left who can answer the question (perhaps, in a long shot, the designer will surface some day in the future, but my investigations came up dry as you can see).