So I finally stumbled, quite randomly, on the source of this.

It was an April Fools joke by Tolkien.Books (MyTolkienBooks.com) on Instagram in 2016.

It was then re-posted by Marcel (@Olwe) on Twitter.

I assume the publishers did think about a BBC tie-in edition, but I imagine it would have been difficult to get the permissions at the time.

Nice to see what could have been.