The film he hated to make
From a recent interview:
KINGSLEY: I actually burned the script. I had a ceremonial burning of the script. The director was such an awful person who was so discourteous to the cast and so amateurish. It was a colossal waste of good energy and time. All actors want to do is please and get it right, and it was so difficult. I burned the script.
Q: And you’ve never said what film that was?
KINGSLEY: [Shakes head no]
(...any guesses which film and director he means?)