Nasrudin (partially found cancelled animated film and early prototype for "The Thief and The Cobbler"; early 1970s)
From The Lost Media Wiki
Before The Thief and the Cobbler, Richard Williams was working on a film called Nasrudin.
The movie would have been based off of a series of books written by Idries Shah (Williams was the illustrator of the books). The books themselves collected the tales of Mulla Nasrudin. Williams had to fund the animated movie by working on television and feature film projects.
By 1972, 3 hours of footage was completed, but Williams had a falling out with the family and Williams abandoned the project. The Shah family took the rights to Williams's illustrations.
The 3 hours of footage that were completed haven't been released. All that exists is just a short clip of the film from a documentary called One Pair of Eyes.