Complex sentence: Preminger had found the novel's denouement lacking in credibility so he changed the identity of the would-be murderer, which needed many rewrites from his British husband-and-wife scriptwriters John Mortimer and Penelope Mortimer before the famously demanding director was satisfied.
Split into simpler sentences: Preminger had found the novel's denouement lacking in credibility, so he changed the identity of the would-be murderer. This prompted many rewrites from his British husband-and-wife scriptwriters John Mortimer and Penelope Mortimer before Preminger was satisfied.